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MIL-STD-1553
TUTORIAL
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Notice: The information that is provided in this documentis believed to be accurate.No
responsibility is assumed by AIM for its use. No license orrights are granted by implication
in connection therewith. Specifications are subject to changewithout notice.
©Copyright 2001-2002 : AIM
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DOCUMENT HISTORY
The following table defines the history of this document. Thedescription ofchanges/enhancements made to each version is definedin general terms.
Version Cover Date Created by Description
1.0 May 26, 2001 Pat Frodyma Creation of document
1.1 May 2001 Pat Frodyma Format Edits
1.2 Feb 2002 Pat Frodyma Edits to Word Descriptions
1.3 Dec 2002 J. Furgerson Format/Edits/Incorporation of Notice1-4 in text
2.3 Nov 2010 B. Waldmann Update addresses
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TABLE OF CONTENTS
Title Page
INTRODUCTION........................................................................................................................1-1
About This Manual.....................................................................................................................1-1
ApplicableDocuments................................................................................................................1-2
MIL-STD-1553 OVERVIEW......................................................................................................2-1
MIL-STD-1553 History and Application...................................................................................2-1
1553B HardwareComponents....................................................................................................2-4
BusController................................................................................................................2-4
Remote Terminal...........................................................................................................2-4
Bus Monitor...................................................................................................................2-5
1553 Cabling...........................................................................................................................2-5
1553 Coupling...........................................................................................................................2-5
DirectCoupling..............................................................................................................2-6
TransformerCoupling....................................................................................................2-6
Bus Topology...........................................................................................................................2-7
MIL-STD-1760C........................................................................................................................2-8
1553 TestProcedures..................................................................................................................2-9
Developmental Testing..................................................................................................2-9
Design Verification........................................................................................................2-9
ProductionTesting.........................................................................................................2-9SystemsIntegrationTesting...........................................................................................2-9
Field/Operational Testing............................................................................................2-10
MIL-STD-1553B SPECIFICATIONINTERPRETATION.........................................................3-1
1. Scope...........................................................................................................................3-1
1.1Scope.......................................................................................................................3-1
1.2Application..............................................................................................................3-1
2. Referenced Documents........................................................................................................3-2
2.1 Issue of Document...................................................................................................3-2
3. Definitions...........................................................................................................................3-34.GeneralRequirements..........................................................................................................3-5
4.1 Test and Operating Requirements.....................................................................3-5
4.2 Data Bus Operation...........................................................................................3-5
4.3 Characteristics...................................................................................................3-6
4.3.1 Dataform...........................................................................................................3-6
4.3.2 BitPriority.........................................................................................................3-6
4.3.3 TransmissionMethod........................................................................................3-7
4.4 Terminal Operation.........................................................................................3-32
4.4.1 CommonOperation.........................................................................................3-32
4.4.2 Bus Controller Operation................................................................................3-33
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4.4.3 RemoteTerminal.............................................................................................3-33
4.4.4 Bus MonitorOperation....................................................................................3-36
4.5 Hardware Characteristics................................................................................3-36
4.5.1 Data Bus Characteristics.................................................................................3-364.5.2Terminal Characteristics.................................................................................3-41
Appendix.........................................................................................................................3-48
10.General..................................................................................................................3-48
20. Referenced Documents.........................................................................................3-50
30. GeneralRequirements...........................................................................................3-50
NOTES.........................................................................................................................................4-1
Acronyms and Abbreviations.....................................................................................................4-1
Definition of Terms....................................................................................................................4-2
APPENDIX A - NOTICES APPLIED TOMIL-STD-1553B....................................................10-1
Notice 1Overview....................................................................................................................10-1
Notice 2Overview....................................................................................................................10-1
Notice 3Overview....................................................................................................................10-2
Notice 4Overview....................................................................................................................10-2
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LIST OF FIGURES
Figure Title Page
3-1 Bus Components...............................................................................................3-1
3-2 DataEncoding...................................................................................................3-7
3-3 WordFormats....................................................................................................3-8
3-4 Command and StatusSync................................................................................3-9
3-5 Data Sync........................................................................................................3-16
3-6 Information Transfer Formats.........................................................................3-23
3-7 Broadcast Information Transfer Formats........................................................3-24
3-8 Intermessage Gap and ResponseTime............................................................3-30
3-9 Data Bus Interface Using TransmforerCoupling............................................3-31
3-10 Data Base Interface Using Direct Coupling....................................................3-31
3-11 CouplingTransmformer..................................................................................3-383-12Terminal Input/Output Characteristics for Transformer Coupled Stubsand
Direct Coupled Stubs......................................................................................3-41
3-13 OutputWaveform............................................................................................3-45
3-10.1 PossibleRedundancy.......................................................................................3-48
3-10.2 PossibleRedundancy.......................................................................................3-48
LIST OF TABLES
Table Title Page
2-I MIL-STD-1553A and MIL-STD-1553B RequirementsComparison......... 2-3
2-II 1553 Cable Characteristics.........................................................................2-5
2-III 1553 Test Plans for allComponents...........................................................2-10
3-I Assigned Mode Codes................................................................................3-11
3-II Criteria for Acceptance or Rejection of a Terminal for theNoise Rejection
Test..............................................................................................................3-44
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MIL-STD-1553 Tutorial
Introduction
INTRODUCTION
About This Manual
This manual was developed to provide a general overview ofMIL-STD-1553 its
specifications and applications.
The first chapter provides a discussion of MIL-STD-1553, itshistory, application and
operational overview. Included is a reference to MIL-STD-1760Cas it applies to Weapon
Stores Interface and its relationship to MIL-STD-1553B.
The second chapter includes a complete annotated version of theMIL-STD-1553B
specification and an interpretation of the specificationcontents. The specification is on the
top of each page and the AIM interpretation is located on thelower portion of the page.
Notices 1 though 4, addendums to the MIL-STD-1553Bspecification, are summarized at the
end of this manual, and have been incorporated into thespecification discussed within this
document.
AIM provides Commercial-Off-The-Shelf (COTS) products to design,produce, integrate, test
and troubleshoot all systems and capabilities mentioned in thisMIL-STD-1553 Tutorial as
well as for ARINC 429, STANAG 3910, MIL-STD-1760 Applicationsand Panavia Serial
Link. Supported hardware platforms include PC/AT, PCI, CompactPCI, VME, VXI, and
PMC.
AIM software products also support full Remote Terminalproduction testing, full bus
analysis and complete system emulation and test capabilities perMIL-STD-1553B
specifications.
For detailed information on AIM solutions, visitwww.aim-online.com or email
[emailprotected]
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Introduction
Applicable Documents
The following documents shall be considered to be a part of thisdocument to the extent
specified herein.
Industry Documents
MIL-STD-464, Electromagnetic Environmental Effects Requirementsfor Systems, March 18,
1997
MIL-HDBK-1553A, Multiplex Application Handbook, March 23,1995
MIL-STD-1553B, Department of Defense Interface Standard forDigital Time DivisionCommand/Response Multiplex Data Bus, Notice1-4, January 1996
MIL-STD-1760C, Interface Standard for Aircraft/Store ElectricalInterconnection System,
March 2, 1999
SAE AS4111, Validation Test Plan for the Digital Time DivisionCommand/Response
Multiplex Data Bus Remote Terminals, October 1998
SAE AS4112, Production Test Plan for the Digital Time DivisionCommand/Response
Multiplex Data Bus Remote Terminals, January 1989
SAE AS4113, Validation Test Plan for the Digital Time DivisionCommand/Response
Multiplex Data Bus Controllers, January 1989
SAE AS4114, Production Test Plan for the Time DivisionCommand/Response Multiplex
Data Bus Controllers, January 1989
SAE AS4115,, Test Plan for the Digital Time DivisionCommand/Response Multiplex Data
Bus System, January 1989
SAE AS4116, Test Plan for the Digital Time DivisionCommand/Response Multiplex DataBus Bus Monitors, September 1990
SAE AS4117, Test Plan for the Digital Time DivisionCommand/Response Multiplex Data
Bus Couplers, Terminators, and Data Bus Cables, March 1991
AIM Product Specific Documents
None
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MIL-STD-1553 Overview
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Data Bus Architecture
MIL-STD-1553 OVERVIEW
MIL-STD-1553B is the military specification defining a DigitalTime Division
Command/Response Multiplexed Data Bus. The 1553 databus is adual-redundant, bi-directional, Manchester II encoded databus witha high bit error reliability. All bus
communications are controlled and initiated by a main buscontroller. Remote terminal
devices attached to the bus respond to controller commands.
MIL-STD-1553B defines specifications for terminal deviceoperation and coupling, word
structure and format, messaging protocol and
electrical characteristics.
MIL-STD-1553 History and Application
MIL-STD-1553B was developed from the growingcomplexity ofintegrated avionics systems and the
subsequent increase in the number of discrete
interconnects between terminal devices. Direct
point-to-point wiring became complex, expensive
and bulky, requiring definition of a multiplex data
bus standard. The first draft of a standard in 1968
by the Aerospace Branch of the Society of AutomotiveEngineers (SAE) laid the foundation
for the US Air Force’s adoption of MIL-STD-1553 in 1973.
A tri-service version, MIL-STD-1553A was released in 1975,modified to MIL-STD-1553Bin 1978 and utilized in the Air Force F-16and the United States (US) Army AH-64A Apache
Attack Helicopter. Notice 2, released in 1986 and supercededNotice 1 released in 1980, is a
tri-service standard for RT design specs and defines how somebus options are to be used.
Notices 3 and 4 did not alter the contents of thestandard, but only provided a title change.
MIL-STD-1553B has become the internationally accepted networkingstandard for integrating
military platforms. Table 2-I shows the differences betweenMIL-STD-1553A and MIL-
STD-1553B.
Military services and contractors originally
adopted MIL-STD-1553 as an avionics data
bus due to its highly reliable, serial, 1 Megabitpersec (Mbps) transfer rate and extremely low
error rate of 1 word fault per 10 million words,
on a dual-redundant architecture.
This reliability has proven equally effective on
communication networks in submarines, tanks,
target drones, missile and satellite systems,
land-based and launch vehicles, and space system including thecurrent International Space
Station and Shuttle programs.
Point-to-Point Wiring Scheme
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MIL-STD-1553B defines the data bus structure for interconnectionof up to 31 remote
terminal (RT) devices. A single controller device on the businitiates the command/response
communication with the remote devices. The remote and controldevices are interconnected
over two, separate buses. Normal operation involves only theprimary bus with the secondarybus available as redundantbackup in the event of primary bus damage or failure.
Standardization of a set of specifications for a military databus provides two major
advantages:
a. Significant size/weight savings of interconnected devices andcabling
b. Reduced development and modification costs withcompatible devices.
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Table 2-I MIL-STD-1553A and MIL-STD-1553B RequirementsComparison
Specification Requirement MIL-STD-1553A MIL-STD-1553BCable TypeJacketed, shielded twisted
pair
Jacketed, shielded twisted
pair
Cable Shield Coverage – minimum 80% 75%
Cable Twist – minimum 12 twists/foot 4 twists/foot
Capacitance, wire to wire – maximum 30 pF/ft 30 pF/ft
Characteristic Cable Impedance (ZO) 70 Ω±10% @ 1 MHz70-80 Ω±10% @ 1 MHz
Nominal
Cable Attenuation 1 dB/100 ft @ 1 MHz 1.5 dB/100 ft @ 1 MHz
Cable Length 300 ft – maximum Unspecified
Cable Termination Characteristic Impedance NominalCharacteristicImpedance ±2%
Cable Stubbing Direct Coupling < 1 ft
Transformer Coupling
1 – 20 ft
Direct Coupling < 1 ft
Transformer Coupling 1 –
20 ft
Cable Coupling Shield Shielded coupler box 75% coverage –minimum
Coupling Transformer Turns Ratio Unspecified 1:141 ±3%with higher
Turns on isolation resistor
side
Transformer Open Circuit Impedance Unspecified 3kΩfrom 75 kHz – 1 MHz
With 1 V RMS sine wave
Transformer Waveform Integrity Unspecified Droop of 20%overshoot –max
Ringing of ±1 V peak –
max
Transformer Common Mode
Rejection
Unspecified 45 dB @ 1 MHz
Fault Isolation
Isolation Resistors in series
with coupler
Direct Coupled
R = 0.75 ZO±5%
R = 0.75 ZO±5%
R = 0.75 ZO±2%
R = 55 Ω±2%
Impedance across bus with failed
Transformer coupling
(Video) What is MIL-STD-1553? | Acromag Solutions Technology Videocomponent
Direct coupling
No less than 1.5 ZO
Unspecified
No less than 1.5 ZO
No less than 110 Ω
Stub Voltage Requirement
Transformer Coupled
Direct Coupled
1 V to 20 V peak to peak
1 V to 20 V peak to peak
1 V to 14 V peak to peak
1.4 V to 20 V peak to peak
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1553B Hardware Components
MIL-STD-1553B defines three types of terminal devices that areallowed on the bus:
a. Bus Controller (BC)
b. Remote Terminal (RT)
c. Bus Monitor (BM).
Bus Controller
The main function of the bus controller (BC) is to provide dataflow control for all
transmissions on the bus. In addition to initiating all datatransfers, the BC must transmit,
receive and coordinate the transfer of information on the databus. All information is
communicated in command/response mode - the BC sends a commandto the RTs, which
reply with a response.
The bus controller, according to MIL-STD-1553B, is the “key partof the data bus system”
and “the sole control of information transmission on the busshall reside with the bus
controller, which shall initiate all transmission”. The bus cansupport multiple BCs, but only
one can be active at a time.
Normal BC data flow control includes transmitting commandsto RTs at predetermined time
intervals. The commands may include data or requests for data(including status) from RTs.The BC has control to modify the flowof bus data based on changes in the operating
environment. These changes could be a result of an air-to-groundattack mode changing to
air-to-air, or the failure mode of a hydraulic system. The BC isresponsible for detecting
these changes and initiating action to counter them. Errordetection may require the BC to
attempt communications to the RT on the redundant, backupbus.
Remote Terminal
The remote terminal (RT) is a device designed to interfacevarious subsystems with the 1553
data bus. The interface device may be embedded within thesubsystem itself, or be an
external interface to tie a non-1553 compatible device to thebus. As a function of theinterface requirement, the RT receives anddecodes commands from the BC, detects any
errors and reacts to those errors. The RT must be able toproperly handle both protocol errors
(missing data, extra words, etc) and electrical errors (waveformdistortion, rise time
violations, etc). RTs are the largest segment of bus components.RT characteristics include:
a. Up to 31 remote terminals can be connected to the databus
b. Each remote terminal can have 31 subadresses
c. No remote terminal shall speak unless spoken to first by thebus controller and
specifically commanded to transmit
Primary Bus (A)
Secondary Bus (B)
Bus
Controller
Remote
TerminalBus
MonitorSubsystem(s)
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Bus Monitor
The bus monitor (BM) listens to all messages on the bus andrecords selected activities. The
BM is a passive device that collects data for real-time or postcapture analysis. The BM canstore all or portions of traffic on thebus, including electrical and protocol errors. BMs are
primarily used for instrumentation and data bustesting.
1553 Cabling
The MIL-STD-1553B definition of a data bus is “a
twisted-shielded pair transmission line made up of a
main bus and a number of attached stubs”.
Shielding limits signal interference from outside
sources and the twisted pair maintains message
integrity through noise canceling.
MIL-STD-1553B specifies that all devices in the
system will be connected to a redundant pair of
buses, providing an alternate data path in the event
of damage or failure of the primary bus path. Bus
messages only travel on one of the buses at a time,
See AlsoMIL-STD-1553 Designer's Guide - [PDF Document]DesignGuide_MILSTD1553 - [PDF Document]3 - System Design - MIL-STD-1553determined by the bus controller.
Properly terminating the main data bus on each end makes the busappear like an infinite line.
Stub loading effects can be minimized on the bus by properlydesigned coupling. Table 2-IIlists the 1553 cablecharacteristics.
1553 Coupling
Coupling connects a terminal device to the main data bus viainterconnecting buses called
stubs. Connecting terminals create a load on the main bus,creating impedance mismatches
and resultant signal reflections that can distort and degradesignal quality on the bus. System
error rate performance and good signal to noise ratio require abalance between stub
impedance being low enough to provide adequate terminal signallevels but high enough to
reduce signal distortion from reflections. MIL-STD-1553B allowstwo methods of coupling
terminal devices to the main bus:
a. Direct coupling
b. Transformer coupling.
Table 2-II 1553 Cable Characteristics
Cable Type Twisted Shielded Pair
Capacitance 30 pF/ft max
CableImpedance 70-85 Ωat 1 MHz
Cable
Attenuation 1.5 dB per 100 ft at 1 MHz max
Twist Ratio 4 per foot min
Shield Coverage 75% min
Cable
Termination Cable Impedance ±2%
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Direct Coupling
Direct coupling connections are wired directly to the buscabling. The isolation
resistors and transformer are internal to the terminal device,not requiringadditional coupling hardware. Direct couplingconnections can only be used with
stub lengths of less than 1 foot.
Isolation resistors provide some protection for the main bus inthe event of a stub
or terminal short, but MIL-STD-1553B cautions the use of directcoupling because
a terminal short could disable the entire bus. Direct stubs canalso cause
significant impedance mismatches on the bus.
Transformer Coupling
Transformer coupling utilizes a second isolation transformer,located external to
the terminal device, in its own housing with the isolationresistors. Transformer
coupling extends the stub length to 20 feet and provideselectrical isolation, better
impedance matching and higher noise rejection characteristicsthan direct
coupling. The electrical isolation prevents a terminal fault orstub impedance
mismatch from affecting bus performance.
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Bus Topology
Bus topology refers to the physical layout and connections ofeach device attached to the data
bus. Single level topologies are the most basic, easy todesign and widely implemented
layouts with all terminal devices connected to a single bus.
Multiple level topologies are designed by interconnecting singlelevel buses so data from one
bus can be transferred on another bus. Busesinterconnected in a multiple level topology can
have equal control over data flow, which helps retain autonomyfor each bus with the greatest
isolation between them. A hierarchical format between multiplelevel buses establishes local
(subordinate) buses and global (superior) buses with the globalbus having control over local,
subordinate buses.
RT RT
Bus A – Primary
Bus B - Secondary
BM
BC RT
Global bus
Vehicle bus
Stores bus
RT
1760C bus
RT
RT
BC
FCC
BC
CDS Bus
FCR
RT
MFDs
RT
HUD
RT
RT
SMS
BC
Weapons
Interface
RTStores
RT RT
RT
Comm
Control
BC
Radio
RT
IFF
RT
NAV
RT
Comm bus
Engines
RT
Hydraulic Electrical
RT
NAV
Management
Navigation bus BC
GPS
RT
INS
RT
SAHR
RT
Mass
Storage
BM
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MIL-STD-1760C
MIL-STD-1760C, released April 15, 1991 defines implementationrequirements for the
Aircraft/Store Electrical Interconnection System (AEIS) betweenaircraft and stores. A store
is any external device attached to the aircraft and includespermanent devices – ECM,
LANTIRN, fuel tanks – and devices designed to separate – bombs,missiles, etc.
MIL-STD-1760C states “the data bus interface shall comply withthe requirements of MIL-
STD-1553” with some additional requirements. In this case, the1553 bus is the controlling
bus over the subordinate 1760 AEIS bus. That 1760 bus maythen control a 1553 bus system
within a store to communicate directly with weapons,navigational aids or communications
subsystems.
The Aircraft Station Interface (ASI) is the connection to theaircraft. Umbilical cabling
connects the ASI to the store connector, the Mission StoreInterface (MSI). The ASI can also
connect – through an umbilical cable – to a Carriage StoreInterface (CSI) to tie in multiple
mission stores. Carriage Store Station Interfaces (CSSI) thenconnects to MSIs via umbilical
cables.
Mission stores contain embedded 1553 RTs that must be capable ofBC-RT, RT-BC and RT-
RT message transfers with the aircraft functioning as the buscontroller. Dynamic bus controlis not allowed on a MIL-STD-1760Cbus design.
Mission Stores
Mission
Store
Aircraft Wing
Aircraft Station
ASI
MSI
Store Station Equipment
ASI
Umbilical
CSI
Carriage Store Equipment
Carriage
CSSI
Umbilical
MSI
Interfaces Controlled by 1760C
ASI – Aircraft Station Interface
CSI – Carriage Store Interface
CSSI – Carriage Store Station Interface
MSI – Mission Store Interface
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1553 Test Procedures
Testing MIL-STD-1553B components validate the functionalcapability of the bus design.
Testing the design of a bus requires testing message formats,mode commands, status word
bits and coupling techniques as they apply to each remoteterminal, bus controller and
monitor device. Five levels of testing have been developed toverify MIL-STD-1553B bus
design compliance:
a. Developmental Testing
b. Design Verification
c. Production Testing
d. Systems Integration Testing
e. Field/Operational Testing.
Developmental Testing
Developmental Testing is implemented at the circuit level todetermine operational capability
of the circuit design. Standard test techniques also validateoperating characteristics over the
required environmental operating range – i.e. temperature,humidity, vibration, etc.
Design VerificationDesign Verification is carried out onpre-production prototypes to insure 1553 compliance, as
well as systems specifications on the design unit itself. Thistesting level verifies
hardware/software requirements before production begins.
Production Testing
Production Testing is performed on production equipment as afinal Quality Assurance check
or during the production process on subassembly items. Oftenapplying a subset of the design
verification tests, Production Testing verifies circuitoperation and proper sequence
operations such as error message validation and mode codeoperation.
Systems Integration Testing
Systems Integration Testing is applied while integrating buscomponents into a system and
insures interoperability of the joined components. DuringSystems Integration Testing,
network hardware and software are combined and assessed toinsure proper data flow control.
Field/Operational Testing
Field/Operational Testing is implemented as a final design testof the system under actual
operating conditions. Known as Developmental Test/OperationalTest – DT/OT – this level
of testing verifies operational integrity of thecomponents/system in installed, fully functionalbusnetworks.
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The Society of Automotive Engineers (SAE) in conjunction withthe government has developed
a series of Test Plans for all 1553 components as listed inTable 2-III.
Table 2-III 1553 Test Plans for all Components
Test Plan Document Number
Remote Terminal Validation Test Plan –
Section 100
MIL-HDBK-1553A
Remote Terminal Validation Test Plan SAE AS4111
Remote Terminal Production Test Plan SAE AS4112
Bus Controller Validation Test Plan SAE AS4113
Bus Controller Production Test Plan SAE AS4114Data Bus SystemTest Plan SAE AS4115
Bus Monitor Test Plan SAE AS4116
Bus Components Test Plan SAE AS4117
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MIL-STD-1553 Specification Interpretation
MIL-STD-1553 Tutorial
MIL-STD-1553B SPECIFICATION INTERPRETATION
The following numbered sections are lifted from MIL-STD-1553Bwith Notices 1-4
incorporated. All Notice 1 changes were superceded by Notice 2changes. Notice 2 changesare noted with two asterisks (**).(Notices 3 and 4 do not affect the body of the text.) Below
each group of numbered sections is an interpretation provided byAIM to aid the reader in a
better understanding of the MIL-STD-1553Bspecification.
1. Scope
1.1 Scope
This standard establishes requirements for digital,command/response, time division
multiplexing (Data bus) techniques**. It encompasses the databus line and its interface
electronics illustrated on Figure 3-1, and also defines theconcept of operation and
information flow on the multiplex data bus and the
electrical and functional formats to be employed.
1.2 Application
When invoked in a specification or statement of
work, these requirements shall apply to the
multiplex data bus and associated equipment which
is developed either alone or as a portion of a**
weapon system or subsystem development. Thecontractor isresponsible for invoking all the
applicable requirements of this Military Standard
(Video) MIL-STD-1553: Overview and Applications Tutorialand any and all subcontractors he may employ.
MIL-STD-1553B defines the requirements for a digital databus and interface requirements.
The original standard addressed only the avionics data busapplications of 1553. The currentrevision, MIL-STD-1553B, Notice 4,has grown to tri-service adoption with applications in
all facets of national and international military craft.
Some sections of the original standard have been modified, firstby Notice 1 – released in
1980 – then were superceded by the publication of Notice 2 in1986. Sections affected by
these releases will be notated in this interpretation.
**Notice 2 changes due to incorporation of tri-serviceapplication which resulted in deletion
of aircraft reference.
Bus
Controller
Remote
Terminal
Subsystem with
Embedded RT
Subsystem(s)
Figure 3-1 – Bus Components
Specification Interpretation
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2. Referenced Documents
2.1 Issue of Document
The following document, of the issue in effect on the date ofinvitation for bid or request for
proposal, forms a part of the standard to the extentspecified herein.
MIL-E-6051 Electromagnetic Compatibility Requirements,Systems
MIL-E-6051 is a Military Standard defining ElectromagneticCompatibility between systems.MIL-STD-1553B referencesMIL-E-6051 in paragraph 4.3.3.2.1 regarding the electrical
characteristics of the main bus data cable. MIL-E-6051 has sincebeen superceded by MIL-
STD-464, Electromagnetic Environmental Effects Requirements forSystems.
MIL-STD-1760C is a Military Standard defining equipmentfor the Aircraft/Store Electrical
Interconnection System (AEIS) between aircraft and stores.Although not mentioned in the
MIL-STD-1553B standard (1760C was issued in 1991), 1553Bis utilized in that standard as
the control path for the stores.
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3. Definitions
3.1 Bit
Contraction of binary digit: may be either zero or one. Ininformation theory a binary digit is
equal to one binary decision or the designation of one of twopossible values or states of
anything used to store or convey information.
3.2 Bit Rate
The number of bits transmitted per second.
3.3 Pulse Code Modulation (PCM)
The form of modulation in which the modulation signal issampled, quantized, and coded so
that each element of information consists of different types ornumbers of pulses and spaces.
3.4 Time Division Multiplexing (TDM)
The transmission of information from several signal sourcesthrough one communication
system with different signal samples staggered in time to form acomposite pulse train.
3.5 Half Duplex
Operation of a data transfer system in either direction over asingle line, but not in both
directions on that line simultaneously.
3.6 Word
In this document a word is a sequence of 16 bitsplus syncand parity. There are three types of
words: command, status and data.
3.7 Message
A single message is the transmission of a command word, statusword, and data words if they
are specified. For the case of a remote terminal to remoteterminal (RT to RT) transmission,
the message shall include the two command words, the two statuswords, and data words.
3.8 Subsystem
The device or functional unit receiving data transfer servicefor the data bus.
3.9 Data Bus
Whenever a data bus or bus is referred to in this document itshall imply all the hardware
including twisted shielded pair cables, isolation resistors,transformers, etc., required to
provide a single data path between the bus controller andall the associated remote terminals.
3.10 Terminal
The electronic module necessary to interface the data bus withthe subsystem and the
subsystem with the data bus. Terminals may exist as separateline replaceable units (LRU’s)
or be contained within the elements of the subsystem.
3.11 Bus Controller (BC)
The terminal assigned the task of initiating informationtransfers on the data bus.
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3.12 Bus Monitor (BM)
The terminal assigned the task of receiving bus traffic andextracting selected information to
be used at a later time.
3.13 Remote terminal (RT)
All terminals not operating as the bus controller or as a busmonitor.
3.14 Asynchronous Operation
For the purpose of this standard, asynchronous operation is theuse of an independent clock
source in each terminal for message transmission. Decoding isachieved in receiving
terminals using clock information derived from the message.
3.15 Dynamic Bus Control
The operation of a data bus system in which designated terminalsare offered control of the
data bus.
3.16 Command/Response
Operation of a data bus system such that remote terminalsreceive and transmit data only
when commanded to do so by the bus controller.
3.17 Redundant Data Bus
The use of more than one data bus to provide more than one datapath between the
subsystems, i.e., dual redundant data bus, tri-redundant databus, etc.
3.18 Broadcast
Operation of a data bus system such that information transmittedby the bus controller of a
remote terminal is addressed to more than one of the remoteterminals connected to the data
bus.
3.19 Mode Code
A means by which the bus controller can communicate with themultiplex bus related
hardware, in order to assist in the management of informationflow.
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4. General Requirements
4.1 Test and Operating Requirements
All requirements as specified herein shall be valid over theenvironmental conditions which
the multiplex data bus system shall be required to operate.
4.2 Data Bus Operation
The multiplex data bus system in its most elementalconfiguration shall be as shown on
Figure 3-1. The multiplex data bus system shall functionasynchronously in a
command/response mode, and transmission shall occur in ahalf-duplex manner. Sole control
of information transmission on the bus shall reside with the buscontroller, which shall initiate
all transmissions. The information flow on the data bus shall becomprised of messages,
which are, in turn, formed by three types of words (command,data, and status) as defined in
4.3.3.5.
The following General Requirements outline Data Bus Operationsas it applies to this
standard.
MIL-STD-1553B defines the data bus system as havingasynchronous, half duplex
communications in a command/response mode.
Command/response mode means that the bus controller initiatesall messages on the bus and
no terminal device transmits to the bus without first beingcommanded to do so.
General information flow on the bus is comprised of messages,made up of three different
types of words: command, data and status.
Word types are defined in 4.3.3.5.
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4.3 Characteristics
4.3.1 Data form
Digital data may be transmitted in any desired form, providedthat the chosen form shall be
compatible with the message and word formats defined in thisstandard. Any unused bit
positions in a word shall be transmitted as logiczeros.
4.3.2 Bit Priority
The most significant bit shall be transmitted first with theless significant bits following in
descending order of value in the data word. The number of bitsrequired to define a quantity
shall be consistent with the resolution or accuracy required. Inthe event that multiple
precision quantities (information accuracy or resolutionrequiring more than 16 bits) are
transmitted, the most significant bits shall be transmittedfirst, followed by the word(s)
containing the lesser significant bits in numerical descendingorder. Bit packing of multiple
quantities in a single data word is permitted.
The Characteristics section of the General Requirements beginsto develop strict guidelines
for word formats, commands, message timing and responsetimes.
Data words transmit 16 bits of data, with the mostsignificant bit (MSB) being transmitted
first. There is no other standard describing the contentof a data word. Content and format
vary from application to application. Most bus architectureshave a self-defined standard for
their particular word formats.
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4.3.3 Transmission Method
4.3.3.1 Modulation
The signal shall be transferred over the data bus in serialdigital pulse code modulation form.
4.3.3.2 Data Code
The data code shall be Manchester II bi-phase level. A logic oneshall be transmitted as a
bipolar coded signal 1/0 (i.e., a positive pulse followedby a negative pulse). A logic zero
shall be a bipolar coded signal 0/1 (i.e., a negative pulsefollowed by a positive pulse). A
transition through zero occurs at
the midpoint of each bit time (see
Figure 3-2).
4.3.3.3 Transmission Bit RateThe transmission bit rate onthe
bus shall be 1.0 Megabit per
second with a combined accuracy
and long-term stability of ±0.1%
(i.e., ± 1000 hertz). The short-
term stability (i.e., stability over
1.0 second interval) shall be at
least 0.01% (i.e., ±100 hertz).
4.3.3.4 Word Size
The word size shall be 16 bits plus
the sync waveform and the parity
bit for a total of 20 bits as shown
on Figure 3-3.
Bits are encoded on a bi-phase Manchester II format. Thisprovides a self-clocking waveform
with equal positive and negative values. Manchester encodinguses the timing and polarity of
the zero crossing point to signal data on the bus, not thevoltage levels of the signal.
Figure 3-2 shows the differences between a Non-Return toZero (NRZ) waveform versus the
Manchester II format. Note that the NRZ does nottransition every bit time.
Manchester waveforms transition at the center of the bittime. A logic 0 goes from negative
to positive during that transition. A logic 1 goes from positiveto negative. With transitions
every bit cycle, the Manchester II provides greater reliabilitythan a typical NRZ waveform.
Specification Interpretation
1 MHz
Clock
Manchester
II
Bi-Phase
Level
NRZ
Data
Figure 3-2 – Data Encoding
(+)
(0)
(-)
(+)
(0)
+
(0)
1 bit time
1 1 10 0 0
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4.3.3.5 Word Formats
The word formats shall be as shown on Figure 3-3 for thecommand, data, and status words.
4.3.3.5.1 Command Word
A command word shall be comprised of a sync waveform, remoteterminal address field,
transmit/receive (T/R) bit, Subaddress/mode field, wordcount/mode code field, and a parity
(P) bit (see Figure 3-3).
BroadcastCommand
DynamicBusControl
TerminalFlag
Figure 3-3 – Word Formats
MessageError
Instrumentation
ServiceRequest
Busy
SubsystemFlag
Parity
1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0
5 5 5 1
16 1
1111115 311 1
1
Sync Remote Terminal
Address
T/R Subaddress
Mode
Data Word Count/
Mode Code
P
Command
Word
Sync Data P
Sync Remote Terminal
Address
Reserved
Data
Word
Status
Word
Note: T/R - transmit/receive
P - parity
Bit
Times
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4.3.3.5.1.1 Sync
The command sync waveform shall be
an invalid Manchester waveform as
shown on Figure 3-4. The width shall bethree bit times, with thesync waveform
being positive for the first one and one-
half bit times, and then negative for the
following one and one-half bit times. If
the next bit following the sync
waveform is a logic zero, then the last
half of the sync waveform will have an
apparent width of two clock periods due
to the Manchester encoding.
4.3.3.5.1.2 Remote Terminal Address
The next five bits following the sync
shall be the RT address. Each RT shall
be assigned a unique address. Decimal address 31 (11111)shall not be assigned as a unique
address. In addition to its unique address, a RT shall beassigned decimal address 31 (11111)
as the common address, if the broadcast option is used.
Command words are transmitted by the bus controller to remoteterminals to instruct them to
receive data, transmit data or perform some other operation.Commands are sent to aid in
data bus management, electrical control of an RT and standarddata transfers. Command
words are only transmitted by the active bus controller.
Each RT connected in a system is assigned a uniqueaddress. With five available address
bits, 25 allows for 32 unique addresses (0-31). The remoteterminal examines the address
field of all incoming commands, and if the address fieldmatches the RT address, that RT acts
on the remainder of the command. RT address 31 (11111) wasdefined as the Broadcast RT.
Individual RTs can enable or disable the processing ofbroadcast messages (a message to allsystem RTs), but no RTcan respond to the broadcast message as a singular RT. Thislimits
the number of RTs in a 1553B bus system to 31, plus thebroadcast address.
Figure 3-4 – Command and Status Sync
Bit
Stream
Data Word Sync Data
Bit Bit
+ VOLTS
- VOLTS
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4.3.3.5.1.3 Transmit/Receive
The next bit following the remote terminal address shall be theT/R bit, which shall indicate
the action required of the RT. A logic zero shall indicate theRT is to receive, and a logic oneshall indicate the RT is totransmit.
4.3.3.5.1.4 Subaddress/Mode
The next five bits following the T/R bit shall be utilized toindicate an RT Subaddress or use
of mode control, as is dictated by the individual terminalrequirements. The
(Video) MIL-STD-1553 Basic TrainingSubaddress/mode values of 0 (00000) and 31 (11111) are reservedfor special purposes, as
specified in 4.3.3.5.1.7, and shall not be utilized for anyother function.
4.3.3.5.1.5 Data Word Count/Mode Code
The next five bits following the Subaddress/Mode field shall bethe quantity of data words to
be either sent out or received by the RT or the optionalmode code as specified in 4.3.3.5.1.7.A maximum of 32 data wordsmay be transmitted or received in any one message block. All
1’s (11111) shall indicate a decimal count of 31, and all 0’s(00000) shall indicate a decimal
count of 32.
4.3.3.5.1.6 Parity
The last bit in the word shall be used for parity over thepreceding 16 bits. Odd parity shall
be utilized.
The T/R bit indicates the action requested of the RT. This bitis set from the RT's perspective,
meaning a 1 bit requests the RT to transmit data, a 0 requeststhe RT to receive data
following the command.
A Subaddress is a function or area within the RT to whichthe command is being directed.
The Subaddress directs the RT to a specific grouping of data tobe transmitted onto the bus,
or it indicates what the RT is to do with the data it is aboutto receive. MIL-STD-1553B sets
aside two special subaddresses: Subaddress 0 and Subaddress 31.They are reserved for
Mode code (or Mode commands).
Mode commands are special messages that utilize thefive-bit Word Count field as a ModeCode field. These messages aresent to specific RTs to check their status, control their
operation and manage the bus. Mode commands exchange at most onedata word, and may
involve no data words at all.
The Data Word Count/Mode Code is another dual function field,determined by the contents
in the Subaddress/Mode field. Up to 32 data words can betransmitted in a message.
Parity checks for bit errors during transmission. Thetotal number of bits for any word
exchanged, excluding the sync bits and including the parity bit,should be odd.
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4.3.3.5.1.7 Optional Mode Control
For RTs exercising this option a
Subaddress/mode code of 0 (00000)or 31 (11111) shall imply thatthe
contents of the data word
count/mode code field are to be
decoded as a five bit mode
command. The mode code shall
only be used to communicate with
the multiplex bus related hardware,
and to assist in the management of
information flow, and not to extract
data from or feed data to a functional
subsystem. Codes 00000 through01111 shall only be used formode
codes which do not require transfer
of a data word. For these codes, the
T/R bit shall be set to 1. Codes
10000 through 11111 shall only be
used for mode codes which require
transfer of a single data word. For
these mode codes, the T/R bit shall
indicate the direction of data word
flow as specified in 4.3.3.5.1.3. Nomultiple data word transfershall be
implemented with any mode code.
The mode codes are reserved for the
specific functions as specified in
Table 3-I and shall not be used for
any other purpose. If the designer
chooses to implement any of these
functions, the codes, T/R bit
assignments, and use of a data word,
shall be used as indicated. The use
of the broadcast command optionshall only be applied toparticular
mode codes as specified in Table 3-
I.
When the Subaddress/Mode field is 0 (00000) or 31 (11111) theWord Count/Mode Code field
identifies the mode code.
Table 3-I – Assigned Mode Codes
Specification Interpretation
T/R Bit
Mode
Code Function
Associated
Data Word
BroadcastCommand
Allowed
1 00000
Dynamic Bus
Control N N
1 00001 Synchronize N Y
1 00010
Transmit Status
Word N N
1 00011 Initiate Self Test N Y
1 00100
Transmitter
Shutdown N Y
1 00101Override
Transmitter N Y
1 00110
Inhibit Terminal
Flag Bit N Y
1 00111
Override Inhibit
Terminal Flag Bit N Y
1 01000 Reset RT N Y
1 01001 Reserved N TBD
1 01111 Reserved N TBD
1 10000
Transmit Vector
Word Y N
0 10001 Synchronize Y Y
1 10010
Transmit Last
Command Y N
1 10011
Transmit BIT
Word Y N
0 10100
Selected
Transmitter Y Y
0 10101
Override Selected
Transmitter Y Y
1 or 0 10110 Reserved Y TBD
1 or 0 11111 Reserved Y TBD
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4.3.3.5.1.7.1 Dynamic Bus Control
The controller shall issue a transmit command to an RT capableof performing the bus control
function. This RT shall respond with a status word as specifiedin 4.3.3.5.3. Control of thedata bus passes from the offering buscontroller to the accepting RT upon completion of the
transmission of the status word by the RT. If the RT rejectscontrol of the data bus, the
offering bus controller retains control of the data bus.
4.3.3.5.1.7.2 Synchronize (without a data word)
This command shall cause the RT to synchronize (e.g., to resetthe internal timer, to start a
sequence, etc.). The RT shall transmit the status word asspecified in 4.3.3.5.3.
4.3.3.5.1.7.3 Transmit Status Word
This command shall cause the RT to transmit the status wordassociated with the last valid
command word preceding this command. This mode command shall notalter the state of thestatus word.
4.3.3.5.1.7.4 Initiate Self Test
This command shall be used to initiate self-test within the RT.The RT shall transmit the
status word as specified in 4.3.3.5.3.
A Dynamic bus control mode command allows the active BC totransfer control of the bus to
a remote terminal device. Acceptance/denial of control resideswith the RT and if accepted,
the RT is promoted to the sole BC on the bus.
Transmit Status Word is utilized by the BC to determine if theRT received the previous
command properly.
Initiate Self Test initiates the RT to perform its Builtin Test (BIT). Usually followed with a
Transmit BIT word mode command to determine the results of thetest. The degree of testing
available from the RT is a function of its design andcapability.
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4.3.3.5.1.7.5 Transmitter Shutdown
This command (to only be used with dual redundant bus systems)shall cause the RT to
disable the transmitter associated with the redundant bus. TheRT shall not comply with acommand to shut down a transmitter on thebus from which this command is received. In all
cases, the RT shall respond with a status word as specified in4.3.3.5.3 after this command.
4.3.3.5.1.7.6 Override Transmitter Shutdown
This command (to only be used with dual redundant bus system)shall cause the RT to enable
a transmitter which was previously disabled. The RT shall notcomply with a command to
enable a transmitter on the bus from which this command isreceived. In all cases, the RT
shall respond with a status word as specified in 4.3.3.5.3 afterthis command.
4.3.3.5.1.7.7 Inhibit Terminal Flag (T/F) bit
This command shall cause the RT to set the T/F bit in the statusword specified in 4.3.3.5.3 tologic zero until otherwise commanded.The RT shall transmit the status word as specified in
4.3.3.5.3.
4.3.3.5.1.7.8 Override Inhibit T/F bit
This command shall cause the RT to override the inhibit T/F bitspecified in 4.3.3.5.1.7.7.
The RT shall transmit the status word as specified in4.3.3.5.3.
4.3.3.5.1.7.9 Reset Remote Terminal
This command shall be used to reset the RT to a power upinitialized state. The RT shall first
transmit its status word, and then reset.
Transmitter Shutdown and Override Transmitter Shutdown are usedonly in a dual redundant
bus system to shut down and restart an RT. The Override commandmust be issued on the
standby or backup bus.
The Inhibit Terminal Flag, when set, indicates a “no fail”condition, regardless of the actual
state of the terminal flag. The BC can use this command toeliminate ongoing error messagesfrom an RT that may besending extraneous or erroneous messages.
Override Inhibit Terminal Flag allows the RT to report itsactual operating condition.
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4.3.3.5.1.7.10 Reserved Mode Codes (01001 to 01111)
These mode codes are reserved for future use and shall not beused.
4.3.3.5.1.7.11 Transmit Vector Word
This command shall cause the RT to transmit a status word asspecified in 4.3.3.5.3 and a
data word containing service request information.
4.3.3.5.1.7.12 Synchronize (with data word)
The RT shall receive a command word followed by a data word asspecified in 4.3.3.5.2. The
data word shall contain synchronization information for the RT.After receiving the
command and data word, the RT shall transmit the status word asspecified in 4.3.3.5.3.
4.3.3.5.1.7.13 Transmit Last Command Word
This command shall cause the RT to transmit its status word asspecified in 4.3.3.5.3followed by a single data word which containsbits 4-19 of the last command word, excluding
a transmit last command word mode code received by the RT. Thismode command shall not
alter the state of the RT’s status word
Transmit Vector Word is related to the Service Request bit inthe status word and determines
specific service requested by the RT.
Synchronization provides the BC a method of establishing acommon timing structure with
RTs. The synchronization can be done with the Command worditself, or with more detail
through an attached Data word.
Transmit Last Command Word is sent by the BC to determine thelast valid command
received by the RT, prior to this mode command. This command isused to determine if errors
exist and assist in data recovery. This mode code does notchange the contents of the last
command or status word. An RT resends the previous status wordwith a data word
containing the previous valid command word received.
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4.3.3.5.1.7.14 Transmit Built-in-Test (BIT) Word
This command shall cause the RT to transmit its status word asspecified in 4.3.3.5.3
followed by a single data word containing the RT BIT data. Thisfunction is intended tosupplement the available bits in the statusword when the RT hardware is sufficiently
complex to warrant its use. The data word, containing the RT BITdata, shall not be altered
by the reception of a transmit last command or a transmitstatus word mode code. This
function shall not be used to convey BIT data from theassociated subsystems(s).
4.3.3.5.1.7.15 Selected Transmitter Shutdown
This command shall cause the RT to disable the transmitterassociated with a specified
redundant data bus. The command is designed for use with systemsemploying more than
two redundant buses. The transmitter that is to be disabledshall be identified in the data
word following the command word in the format as specified in4.3.3.5.2. The RT shall not
comply with a command to shut down a transmitter on the bus fromwhich this command isreceived. In all cases, the RT shall respondwith a status word as specified in 4.3.3.5.3.
4.3.3.5.1.7.16 Override Selected Transmitter Shutdown
This command shall cause the RT to enable a transmitter whichwas previously disabled. The
command is designed for use with systems employing more than tworedundant buses. The
transmitter that is to be enabled shall be identified in thedata word following the command
word in the format as specified in 4.3.3.5.2. The RT shall notcomply with a command to
enable a transmitter on the bus from which this command isreceived. In all cases, the RT
shall respond with a status word as specified in 4.3.3.5.3.
4.3.3.5.1.7.17 Reserved Mode Codes (10110 to 11111)
These mode codes are reserved for future use and shall not beused.
Transmit BIT Word provides the BC with the selected RT's Builtin test results. This command
allows error recovery procedures without changing the error datarecorded in the word.
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4.3.3.5.2 Data Word
A data word shall be comprised of a sync waveform, data bits,and a parity bit (see Figure 3-
3).4.3.3.5.2.1 Sync
The data sync waveform shall be an invalid
Manchester waveform as shown on Figure
3-5. The width shall be three bit times, with
the waveform being negative for the first
one and one-half bit times, and then
positive for the following one and one-half
bit times. Note that if the bits preceding
and following the sync are logic ones, then
the apparent width of the sync waveformwill be increased to fourbit times.
4.3.3.5.2.2 Data
The sixteen bits following the sync shall be
utilized for data transmission as specified in
4.3.2.
4.3.3.5.2.3 Parity
The last bit shall be utilized for parity as
specified in 4.3.3.5.1.6.
Data words contain the actual information and can betransmitted by a BC or an RT
Data words are transmitted by a BC, or by an RT inresponse to a BC request. Data words
may also be sent between two RTs. MIL-STD-1553B allows a maximumof 32 data words to
be sent in a packet with a command word. Data words contain themost information of thethree words and are the least structuredwords in MIL-STD-1553B.
The Data word sync is unique. The command and status word syncpattern is the same.
Data Word Sync Data
Bit Bit
Figure 3-5 – Data Sync
Bit
Stream
+ VOLTS
- VOLTS
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4.3.3.5.3 Status Word
A status word shall be comprised of a sync waveform, RT address,message error bit,
instrumentation bit, service request bit, three reserved bits,broadcast command received bit,busy bit, subsystem flag bit,dynamic bus control acceptance bit, terminal flag bit, and aparity
bit. For optional broadcast operation, transmission of thestatus word shall be suppressed as
specified in 4.3.3.6.7.
4.3.3.5.3.1 Sync
The status sync waveform shall be as specified in4.3.3.5.1.1.
4.3.3.5.3.2 RT Address
The next five bits following the sync shall contain the addressof the RT which is transmitting
the status word as defined in 4.3.3.5.1.2.
Status words are transmitted by a remote terminal in response toan error free, nonbroadcast
command. Status words relay conditional information about theRT, errors detected by the
RT in the command or data sent from the BC, or an RTrequest for service. Status words are
only transmitted by RTs after receiving a command from a BC.
The purpose of transmitting the RT address in a status responseallows the BC to verify thecorrect RT is responding and preventsany other RT from mistaking the status response as a
command (the sync pattern for both is the same) due to differentaddresses.
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4.3.3.5.3.3 Message Error Bit
The status word bit at bit time nine (see Figure 3-3) shall beutilized to indicate that one or
more of the data words associated with the preceding receivedcommand word from the buscontroller has failed to pass the RT’svalidity test as specified in 4.4.1.1. This bit shall also be
set under the conditions specified in 4.4.1.2, 4.4.3.4, and4.4.3.6. A logic one shall indicate
the presence of a message error, and a logic zero shall show itsabsence. All RTs shall
implement the message error bit.
4.3.3.5.3.4 Instrumentation Bit
The status word at bit time ten (see Figure 3-3) shall bereserved for the instrumentation bit
and shall always be a logic zero. This bit is intended to beused in conjunction with a logic
one in bit time ten of the command word to distinguish between acommand word and a
status word. The use of the instrumentation bit is optional.
The Message Error Bit is used by the RT to indicate an error inthe command or data word
transmission from the BC. The Message Error bit is set to alogic 1 when any of the
following conditions occur:
a. A data word received from the BC contains an error
b. A gap is detected between data words
c. The RT does not recognize a received command
(Video) How Do I Set up MIL-STD-1553 Bus Decode?d. The wrong number of data words is received by the RT.
If the RT detects an error, the Message Error bit is set,but the status word is not sent. The
BC must send a “Transmit Last Status” mode command todetermine the reason for no
response. After receiving this mode command, the RT transmitsthe Status word with the
Message Error bit set. The Message Error bit remains setto a logic 1 until a new valid
command, other than “Transmit Last Status”, is received by thisRT.
The Instrumentation bit is used to differentiate between commandand status words.
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4.3.3.5.3.5 Service Request Bit
The status word bit at bit time eleven (see Figure 3-3) shall bereserved for the service request
bit. The use of this bit is optional. This bit when used,shall indicate the need for the buscontroller to take specificpredefined actions relative to either the RT or associated
subsystems. Multiple subsystems, interfaced to a single RT,which individually requires a
service request signal shall logically OR their individualsignals into the single status word
bit. In the event this logical OR is performed, then thedesigner must make provisions in a
separate data word to identify the specific requestingsubsystems. The service request bit is
intended to be used only to trigger data transfer operationswhich take place on a exception
rather than periodic basis. A logic one shall indicate thepresence of a service request, and a
logic zero its absence. If this function is not implemented, thebit shall be set to zero.
4.3.3.5.3.6 Reserved Status Bits
The status word bits at bit times twelve through fourteen arereserved for future use and shallnot be used. These bits shall beset to a logic zero.
4.3.3.5.3.7 Broadcast Command Received Bit
The status word at bit time fifteen shall be set to a logic oneto indicate that the preceding
valid command word was a broadcast command and a logic zeroshall show it was not a
broadcast command. If the broadcast command option is notused, this bit shall be set to a
logic zero.
The Service Request bit indicates the RT requires service. Thisbit can also be set to direct the
BC to initiate a predefined data transfer or modecommand.
The Broadcast Command Received bit indicates the RT received avalid broadcast command.
This bit is set to a logic 1 when a broadcast message isreceived and remains set until the RT
transmits the status word or receives a valid, non-broadcastcommand. The BC can use this
bit to determine if a broadcast command was received error freeby requesting the status
word to be sent. The use of this bit is optional and is clearedto a logic 0 if not utilized.
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4.3.3.5.3.8 Busy Bit
The status word bit at bit time sixteen (see Figure 3-3) shallbe reserved for the busy bit. The
use of this bit is optional. This bit, when used, shall indicatethat the RT or subsystem isunable to move data to or from thesubsystem in compliance with the bus controller’s
command. A logic one shall indicate the presence of a busycondition, and a logic zero its
absence. In the event the busy bit is set in response to atransmit command, then the RT shall
transmit its status word only. If this function is notimplemented, the bit shall be set to logic
zero.
4.3.3.5.3.9 Subsystem Flag Bit
The status word bit at bit time seventeen (see Figure 3-3) shallbe reserved for the subsystem
flag bit. The use of this bit is optional. This bit, when used,shall flag a subsystem fault
condition, and alert the bus controller to potentially invaliddata. Multiple subsystems,
interfaced to a single RT, which individually require asubsystem flag bit signal shall logicallyOR their individualsignals into the single status word bit. In the event this logicalOR is
performed, then the designer must make provisions in aseparate data word to identify the
specific reporting subsystem. A logic one shall indicate thepresence of the flag, and a logic
zero its absence. If not used, this bit shall be set to logiczero.
4.3.3.5.3.10 Dynamic Bus Control Acceptance Bit
The status word bit at bit time eighteen (see Figure 3-3) shallbe reserved for the acceptance
of dynamic bus control. This bit shall be used if the RTimplements the optional dynamic bus
control function. This bit, when used, shall indicate acceptanceor rejection of a dynamic bus
control offer as specified in 4.3.3.5.1.7.1. A logic one shallindicate acceptance of control,and a logic zero shall indicaterejection of control. If not used, this bit shall be set tologic
zero.
The Busy bit indicates the RT is unable to transfer data. Set toa logic 1 when the RT is
unable to move data to or from the terminal device in responseto a BC command, this bit
stays set as long as the busy condition exists. The use ofthis bit is optional and is cleared to
a logic 0 if not utilized.
The Subsystem Flag bit is used by the RT to alert the BC that asubsystem fault exists and the
data transmitted may be invalid. Set to a logic 1 to indicate afault condition, the bit remains
set until the subsystem fault is resolved. The use of thisbit is optional and is cleared to a
logic 0 if not utilized.
The Dynamic Bus Control Acceptance bit is used by the RT toindicate to the BC that this RT
has accepted the dynamic Bus Control command. This immediatelytransfers control of the
bus to this RT, which now acts as the backup bus controller. Ifthe RT rejects dynamic bus
control, the bit is reset to a logic 0. Upon transmission of thestatus word, the bit is cleared.
The use of this bit is optional and is cleared to a logic 0 ifnot utilized.
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4.3.3.5.3.11 Terminal Flag Bit
The status word bit at bit time nineteen (see Figure 3-3) shallbe reserved for the terminal flag
function. The use of this bit is optional. This bit, when used,shall flag a RT fault condition.A logic one shall indicate thepresence of the flag, and a logic zero, its absence. If notused,
this bit shall be set to logic zero.
4.3.3.5.3.12 Parity Bit
The least significant bit in the status word shall be utilizedfor parity as specified in
4.3.3.5.1.6.
4.3.3.5.4 Status Word Reset
The status word bit, with the exception of the address, shall beset to logic zero after a valid
command word is received by the RT with the exception asspecified in 4.3.3.5.1.7. If the
condition which caused bits in the status word to be set (e.g.,terminal flag) continue after thebits are reset to logiczero, then the affected status word bit shall be again set, andthen
transmitted on the bus as required.
The Terminal Flag bit indicates a fault in the RT itself. Thebit is set to a logic 1 until the
fault is resolved. The use of this bit is optional and iscleared to a logic 0 if not utilized.
The Parity bit is used on each word to identify bit errorsduring transmission. This odd
parity check will detect an odd number of bit errorsoccurring in a word.
Status Word Reset is a command issued to reset the Status Codefield of the status word. This
prevents a condition being reported longer than itactually exists. Receiving a valid message
or mode command will reset the RT's status word, except TransmitStatus Word and Transmit
Last Command Word. Neither of these mode codes will changethe bits in the Status Code
field of the last valid command word.
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4.3.3.6 Message Formats
The messages transmitted on the data bus shall be in accordancewith the formats on Figure
3-6 and Figure 3-7. The maximum and minimum response times shallbe as stated in 4.3.3.7and 4.3.3.8. No message formats, other thanthose defined herein, shall be used on the bus.
MIL-STD-1553B defines 10 types of messages to betransmitted over the bus as shown in
Figures 3-6 and 3-7. Each message is composed of controlwords (command and status) and
data words, and is always initiated with a BC command.
Normal command/response communications, as shown in Figure3-6, start with a commandfrom the BC, transmitted to aselected RT address. The RT receives or transmits data -
depending on the BC command - and transmits a status wordresponse if the transmission is
valid and received error-free. The BC can also initiate anInformation transfer between two
RTs by issuing one a Transmit command and the other, aReceive.
Mode commands, as shown in Figures 3-6 and 3-7, are usedin terminal control and systems
checks. Mode commands may or may not involve the transfer of adata word.
Broadcast commands, as shown in Figure 3-7, are commandssent to multiple RTs at once.
Although restricted under Notice 1, Notice 2 allowsbroadcast command transmissions butonly the broadcast mode commandsshown in Table 3-I. The RT is responsible for
distinguishing between broadcast and non-broadcast commandmessages. An RT address of
11111 (31) indicates a broadcast message.
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Figure 3-6 – Information Transfer Formats
Receive
Command
Transmit
Command
Status
Word
Data
Word
Data
Word
Data
Word
Status
Word
Next
CommandRT to RTTransfer
Mode
CommandStatus
WordNext
Command
Mode Command without Data Word
Mode
CommandStatus
WordNext
Command
Mode Command with Data Word (Transmit)
Data
Word
Note:
# Intermessage Gap
* * Response Time
Mode
CommandStatus
WordNext
Command
Mode Command with Data Word (Receive)
Data
Word
Transmit
CommandStatus Word Data
WordData
WordData
WordNext
Command
RT to Controller Transfer
Receive
CommandData
WordData
WordData
Word
Status
Word
Next
Command
Controller to RT Transfer
••• * * #
•••* * #
•••* * #* *
* * #
* * #
* * #
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Figure 3-7 – Broadcast Information Transfer Formats
Receive
CommandTransmit
Command
Status
WordData
Word
Data
WordNext
Command
RT to RT s Broadcast
Mode
CommandNext
Command
Mode Command without Data Word
Mode
CommandNext
Command
Mode Command with Data Word (Receive)
Data
Word
Receive
CommandData
WordData
WordData
Word
Next
Command
Controller to RT(s) Broadcast
Data
Word
Note:
# Intermessage Gap* * Response Time
•••
**
#
•• #
#
#
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4.3.3.6.1 Bus Controller to Remote Terminal Transfers
The bus controller shall issue a receive command followed by thespecified number of data
words. The RT shall, after message validation, transmit a statusword back to the controller.
The command and data words shall be transmitted in a contiguousfashion with no interwordgaps.
4.3.3.6.2 Remote Terminal to Bus Controller Transfers
The bus controller shall issue a transmit command to the RT. TheRT shall, after command
word validation, transmit a status word back to the buscontroller, followed by the specified
number of data words. The status and data words shall betransmitted in a contiguous fashion
with no interword gaps
BC-RT
In this most common informational transfer, the BC sendsdata to an RT. The message begins
with a command word with the T/R bit reset to a logic 0 toindicate the RT is to receive data.
The value set in the Data Word Count/Mode Code field of thecommand word tells the RT
how many data words will be transmitted after the command word.There is no gap between
the command word and the data word, or between data wordsthemselves.
The receiving RT validates the incoming message and, if themessage is valid and legal,
responds with a status word acknowledging message receipt.
RT-BC
This informational exchange involves the BC requesting an RT tosend data back. The
message begins with a command word with the T/R bit set to alogic 1 to initiate the RT to
transmit data. The value set in the Data Word Count/Mode Codefield of the command word
indicates the number of data words the RT is to transmit.
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4.3.3.6.3 Remote Terminal to Remote Terminal Transfers
The bus controller shall issue a receive command to RT Afollowed contiguously by a
transmit command to RT B. RT B shall, after command validation,transmit a status wordfollowed by the specified number of datawords. The status and data words shall be
transmitted in a contiguous fashion with no gap. At theconclusion of the data transmission
by RT B, RT A shall transmit a status word within thespecified time period.
RT-RT
This exchange of data is again initiated by the BC, but involvesa transfer of information
between two RTs. The BC directs this transfer by sending twoback-to-back commands.
First, a Receive command is sent to the receiving RT, withthe T/R bit reset to a logic 0 for
Receive, and the Data Word Count/Mode Code fieldindicating the number of words to
accept.
Second, without any gap between commands, a Transmit command issent to the transmitting
RT with the T/R bit set to a logic 1. The Data WordCount/Mode Code field indicates the
number of words to transmit.
The Address field in the Receive and Transmit command wordscontains the address of thereceiving and transmitting RTs andshould always be different. The Data Word Count/Mode
Code fields in both words have to be the same for the transferto be successful.
The transmitting RT responds to the Transmit command by sendinga status word to the
Receiving RT with the appropriate number of data words.The receiving RT responds with a
status word acknowledging receipt of the valid, error-freemessage.
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4.3.3.6.4 Mode Command without Data Word
The bus controller shall issue a transmit command to the RTusing a mode code specified in
Table 3-I. The RT shall, after command word validation, transmita status word.4.3.3.6.5 Mode Command with Data Word (Transmit)
The bus controller shall issue a transmit command to the RTusing a mode code specified in
Table 3-I. The RT shall, after command word validation, transmita status word followed by
one data word. The status word and data word shall betransmitted in a contiguous fashion
with no gap.
4.3.3.6.6 Mode Command with Data Word (Receive)
The bus controller shall issue a receive command to the RT usinga mode code specified in
Table 3-I, followed by one data word. The command word and dataword shall be transmitted
in a contiguous fashion with no gap. The RT shall, after commandand data word validation,transmit a status word back to thecontroller.
Mode command messages are sent from the BC to an RT tocontrol its operation, check its
operating status or perform general data bus management. For acommand from the BC to
be recognized by the RTs as a mode command, the Command WordSubaddress/Mode field in
the command word has to be set to 0 (00000) or 31 (11111). Withthat designation, the Data
Word Count/Mode Code field now contains the mode code for thecommand to be
(Video) MIL-STD-1553 Tutorial - part 1 | Excalibur Systemsimplemen
Mil Std 1553B - [PDF Document] (2023)
Videos
1. Zoom course on MIL-STD-1553 | Excalibur Systems
(ExcaliburSystems)
2. UEI Technical Master Class: 1553 (MIL-STD-1553) Bus Controller
(United Electronic Industries)
3. A Complete 1553 Solution from United Electronic Industries (BC, RT and BM)
(United Electronic Industries)
4. ARINC629 | ARINC708 | ARINC573 | MIL-STD-1553B | MIL-STD-1773B
(Unique aviation)
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6. ARINC429 | Data bus | word format | BPRZ | slew rate
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