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NSBE Seminar 1
MIL-STD 1553on the International Space Station’s
Command and Data Handling System
NSBE training seminarSeptember 25, 2003P.Eugene Jackson Jr.
NSBE Seminar 2
Command and Data Handling System (C&DH)
C&DH Facts: 54 Multiplexer DeMultiplexers ((MDM) – ESSMDM & SSMDM)100 + MIL-STD-1553 data buses A/B channel redundancy1200 + MIL-STD-1553 remote terminal (RT) address assignments
• 190 payload 1553 RT addresses• 600 + International partners and firmware controller 1553 devices• 90 unique types devices
100 (approximately) Software Interface Control Documents
ESSMDMs and SSMDMs are used in the Space Station Command and Data Handling system design which is a “layered” approach providing difference levels of processing and communication capabilities for each layer. The ESSMDM provide control and data processing, communication control, and mass resources to support control and management function of onboard functions. The SSMDM are used to provide embedded control processing at the lower level and at the main interface to on board sensors and effectors via analog and discrete input/output.
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Both MDM type are designed to host User Application Software (UAS) to control all functionally. Functional Space Station Architecture (figure on the left) represents a”vertical slice” of The C&DH system defining the Control Processing, Local Processing, and the User Processing as they relate to MDMs. The top two layers, the Control Buses and theLocal Buses are often referenced to as Local Bus. The lower layer of MIL-STD-1553 is referenced As User Bus layer, because the communicate Can be either Local bus protocol or a custom User Protocol connected directly to the user equipment.
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Architecture Overview• Data Rate 1 MHz
• Word Length 20 bits/word
• Data Bits/Word 16 bits
• Transmission Technique Half-duplex
• Operation Asynchronous, self-clocking waveform
• Encoding Manchester II bi-phase
• Bus Topology Linear multi-drop bus, with stub-coupledterminals
• Bus Coupling Transformer or direct coupled
• Transmission Media Twisted-shielded-pair cable terminatedin its characteristic impedance
• Protocol Time-division, command/response
• Bus Control Single or multiple
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MIL-STD-1553 Simple Multiplex Architecture
Subsystemwith
EmbeddedRemoteTerminal
RemoteTerminal
Subsystem(s)
BusController
OptionalRedundantCables
Cable
Coupler
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Bus Topology Examples
BusController
Single LevelTopology
Single Level,with Functional
Separation
Sensor A Sensor B
Comp 1
Sensor C
Bus ABus B
Sensors
Sensors
Bus ABus BBus ABus B
Bus ABus B
Sensors
Controls andDisplay Bus
NavigationBus
StoresBus
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Transformer Coupled Bus Network
Main BusZo Zo
R = 0.75 • Zo ohm
Terminal1
Terminal2
TerminalN
R R R R R R
1 1 1
1.41 1.41 1.41
Stubs
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Transmission Line Characteristics
• Cable Type Twisted-shielded-pair
• Capacitance 30 pFd./ft Max
• Characteristic 70 to 85 OHMS at 1 MHz, nominal Impedance (actual, per notice 2)
• Attenuation 1.5 db/100 ft Max at 1MHz
• Bus Length Not specified in 1553B (300 ft suggested max)
• Stub Length Direct coupled - less than 1 ft Transformer coupled - 20 ft (suggested max)
• Termination Ends terminated with resistors of Z0 +/-2%
• Cable Shielding 75% coverage (90% coverage, per notice 2)
1553 Requirement
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Bus Coupler Characteristics
DirectCoupled
TransformerCoupled
Shield
Data Bus
R R
1:1.41
55 ohm2%
55 ohm2%
Transceiver Transceiver
Terminal Terminal
• Isolation resistors: R = 0.75 ZO 2%• Isolation transformer: turns
ratio 1:1.41 3%(1 – terminal winding)(1.41 – bus winding)ZOC > 3K at 75 kHz to 1 MHz1V rms sine wave
Droop: < 20%Overshooting/ringing: < 1VCMR: > 45 dB at 1 MHz
• Nominal characteristic impedance of bus cable:ZO = 70 to 85 at 1 MHz
At 27v P-P 250-kHzsq wave
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Data Bus Networks—Stub Impedance vs. Length
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
020 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Direct Coupled
Stub Length (ft)
Stu
b I
mp
eda
nce
, Z
1 (
oh
ms)
Transformer Coupled(Ideal Transformer)
Transformer Coupled(1553B Transformer)
Direct Coupled(Z1 = 2000 ohms)
•Terminal input impedance (Z1): 1000 ohms, except where noted•Coupler transformer: 1:1.41 turns ratio• Isolation resistors: 52.5 ohms•Cable capacitance: 30 pF/ft
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MIL-STD-1553 Data Encoding
One Bit Time
(+) –
(0) –
(+) –
(0) –
(+) –
(0) –
(-) –
1 MHzClock
NRZData
ManchesterII
Bi-Phase L
1 0 1 1 0 0 0
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MIL-STD-1553B Intermessage Gap and Response Timing
Command/Status SyncParity Bit
Bit Time Bit Time
19 20 1 2 3
+ Volts
0
– Volts
Gap Time: Min 4.0 microsec Response Time: Min 4.0 microsecMax 12.0 microsec
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MIL-STD-1553B Word Formats
• Command Word– Command/status sync, 16 data bits, odd party– Transmitted only by the active bus controller– Contains unique address of RT or broadcast address (11111)– Contains transmit or receive data indicator– Contains subaddress (or mode code indicator)– Contains word count of 1 to 32 (or mode code)
• Status Word– Command/status sync, 16 data bits, odd party– Transmitted only by the commanded remote terminal– Contains own address and terminal health information
• Data Words– Data word sync, 16 data bits, odd parity– Transmitted or received by bus controllers or remote terminals– Received by bus monitors
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MIL-STD-1553B Word Formats
1 201918171615141312111098765432
5 1 5 5 1
P
1
P
16
5 1 1 1 3 1 1 1 1 1 1
Remote TerminalAddress
Subaddress/Mode
Data WordCount/Mode Code
Sync
Sync
Sync Remote TerminalAddress
Bit Times
Command Word
Data Word
Status Word
T/R
Data
Reserved
Bro
ad
ca
st C
om
ma
nd
Re
ce
ive
d
Bu
sy
Su
bs
ys
tem
Fla
g
Dy
na
mic
Bu
s C
on
trol
Ac
ce
pta
nc
e
Te
rmin
al F
lag
Pa
rity
Se
rvic
e R
eq
ue
st
Ins
trum
en
tatio
n
Me
ss
ag
e E
rror
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Information Transfer Formats
ReceiveCommand
DataWord
DataWord
DataWord
StatusWord
CommandWord
Controller-to-RT Transfer
TransmitCommand
StatusWord
DataWord
DataWord
DataWord
CommandWord
RT-to-ControllerTransfer
ReceiveCommand
TransmitCommand
StatusWord
DataWord
DataWord
DataWord
StatusWord
CommandWord
RT-to-RTTransfer
ModeCommand
StatusWord
CommandWord
Mode CommandWithout DataWord
ModeCommand
StatusWord
DataWord
CommandWord
Mode CommandWith Data Word(Transmit)
ModeCommand
DataWord
StatusWord
CommandWord
Mode CommandWith Data Word(Receive)
Next
Next
Next
Next
Next
Next
#
#
#
#
#
#
• • • •
• • • •
• • • •
• •
• •
• • • •
• •
• •
• •
Intermessage gap
Response time
#
• •
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ReceiveCommand
TransitCommand
StatusWord
DataWord
DataWord
DataWord
CommandWord
RT-to-RTTransfer • • • •• • #
Broadcast Information Transfer Formats
ReceiveCommand
DataWord
DataWord
DataWord
CommandWord
Controller-to-RT(s) Transfer
ModeCommand
CommandWord
Mode CommandWithout DataWord
ModeCommand
DataWord
CommandWord
Mode CommandWith Data Word
Next
Next
Next
• • • • #
#
#
Intermessage gap
Response time
#
• •
Next
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MIL-STD-1553B Terminal Block Diagram
Computer
SubsystemI/F
EncodeDecode
I/OProcessPower Supply
Transceiver
Transceiver
InternalBuses
1553 Terminal1553B Data Bus
Subsystem
Subsystem
Subsystem
Memory
EncodeDecode
Protocol Control
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Generalized 1553B Terminal Functions
DSubsystem
InterfaceCircuits
Subsystemor Host
ProcessorInterface
Data BusInterface
CWord/
MessageProcessor
BBit/Word
Processor(Encoder/Decoder)
AAnalog
Transmit/Receive
Word Processor
• Receive–Signal limiting–Filter–Threshold
detection• Transmit
–Driver–Transmitter
control–Timer
• Common–Bus coupling
•Receive–Receiver–Sync detection–Data detection–Manchester error
detection–Parity check–Bits and word count
•Transmit–Transmit control–Sync and data
encoder–Parity generation
•Clock generation
•Receive–Command word
code–Status word decode–Address recognition–Mode execution–Word count
recognition–Message error
detection•Transmit–Word count (BC)–Status register
•Built-in test•Subsystem interface control–Data address–Control registers
•Memory buffers
•Channel selection•Data sampling•Conversation•Subsystem timing•Buffer registers•Calibration•Self-test•DMA to host memory
• Interrupt lines•Control lines
Message Processor
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GNC2 Local Bus – PRESTO analysis
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GNC2 Local Bus – PRESTO analysis - result
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JEM Local Bus – PRESTO analysis (1 of 2)
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JEM Local Bus – PRESTO analysis (2 of 2)
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JEM Local Bus – PRESTO analysis - result
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Requirement: all ORUs connecting to ISS cross-boundary buses must meetMIL-STD-1553B, Notice 2.
Purpose: to verify that Remote Terminal designed to meet the requirements of MIL-STD-1553B, Notice 2. Test will be performed on stand-alone ORU.
• Physical Layer: input and output electrical characteristics, noise rejection.• Protocol Layer: subaddress legalization, error detection and handling, transmission rate, mode code implementation …..
Test Plan: Appendix A of MIL-HDBK-1553 or Section 100 of MIL-HDBK-1553A.
Test Duration: 2 working days allocated for each RT.
Mil-Std-1553Remote Terminal Validation Testing
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ORUTest SupportEquipment
Main Power
BUS TESTERPC and TestEquipment
TYPICAL TEST SET-UP
AddressBox
6
A
B
Main Power
Mil-Std-1553Remote Terminal Validation Testing
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Control Moment Gyroscopes
CMG – FactsThe speeds available for commanding: 6269, 6319, 6364, 6410, 6456, 6504, 6552, 660, 6639, 6683, 6722, 67686808, 6849, 6890, and 6932 rpm.The spin motor is used to spin up the wheel and maintain a constant wheel speed. At a nominal line voltage of 120 vdc, the maximum possible wheel speed is 8290 rpm.Gimbal Torquers – Used to rotate the gimbal assembly.CMG health and status – Temperatures, electronics voltages, inner and out gimbals positions and rates …
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Control Moment Gyroscope (CMG) interface
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Control Moment Gyroscope (CMG) interface
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Control Moment Gyroscope (CMG) interface
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Control Moment Gyroscope (CMG) interface
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Useful web links
Command and Data Handling Architecture Control Document (D684-10500-02) http://iss-www.jsc.nasa.gov/ss/issapt/cdhait/resources/add_master15.PDF Command and Control Software site: http://iss-www.jsc.nasa.gov/ss/issapt/vehipt/sspt7ipt/cdhipt/ccipt/grp/ccsdev/ccs.htm
MIL STD 1553 tutorial
http://www.condoreng.com/support/downloads/tutorials/index.shtml
MDM User’s Guide ( Volume I) X8264868, Rev D
MIL-STD-1553 Details drawing contributed by:Mack McCall, Boeing
Primus E. Jackson Jr. [email protected] 281 488 5551 cell 281 788 7663
.
