GR716-DS-UM, May 2019, Version 1.29
178
www.cobham.com/gaisler
GR716
MIL-STD-1553B (and derived standard SAE AS15531) is a bus standard for transferring data
between up to 32 devices over a shared (typically dual-redundant) differential wire. The bus is
designed for predictable real-time behavior and fault-tolerance. The raw bus data rate is fixed at 1
Mbit/s, giving a maximum of around 770 kbit/s payload data rate.
One of the terminals on the bus is the Bus Controller (BC), which controls all traffic on the bus. The
other terminals are Remote Terminals (RTs), which act on commands issued by the bus controller.
Each RT is assigned a unique address between 0-30. In addition, the bus may have passive Bus Moni-
tors (BM:s) connected.
There are 5 possible data transfer types on the MIL-STD-1553 bus:
•
BC-to-RT transfer (“receive”)
•
RT-to-BC transfer (“transmit”)
•
RT-to-RT transfer
•
Broadcast BC-to-RTs
•
Broadcast RT-to-RTs
Each transfer can contain 1-32 data words of 16 bits each.
The bus controller can also send “mode codes” to the RTs to perform administrative tasks such as time
synchronization, and reading out terminal status.
23.2
Electrical interface
The core is connected to the MIL-STD-1553B bus wire through single or dual transceivers, isolation
transformers and transformer or stub couplers as shown in figure 31. If single-redundancy is used, the
unused bus receive P/N signals should be tied both-high or both-low. The transmitter enables are typ-
ically inverted and therefore called transmitter inibit (txinh).
23.3
Operation
23.3.1 Operating modes
The core contains three separate control units for the Bus Controller, Remote Terminal and Bus Mon-
itor handling, with a shared 1553 codec.
rxenA
txA_N
rxA_P
rxA_N
txA_P
txinhA
Bus A
rxenB
txB_N
rxB_P
rxB_N
txB_P
txinhB
Bus B
GR1553B
Terminal boundary
Figure 31.
Interface between core and MIL-STD-1553B bus (dual-redundant, transformer coupled)
