MIL-STD-1553 is a message transmission-based bus that defines ten different message types. Most message formats consist of Command words, Status words, and Data words. These words enable communication between system elements.
The bus controller initiates and controls all bus communications, while remote terminal devices attached to the bus respond to the controller’s commands.
The standard defines specifications for terminal devices.
Here are some terms related to MIL-STD-1553:
- Bus Monitor
CA bus monitor can be configured to receive words from either one or both dual redundant 1553 buses. Bus monitors are passive listeners on 1553 buses. They receive and store words received from the bus but never transmit.
- Command Word
A type of word transmitted by a bus controller. Its 16 bits include the remote terminal’s 5-bit address, 5-bit subaddress, and a 5-bit word count. There is also a bit to indicate if the remote terminal receiving the Command word will either receive or transmit data.
- Data Word
All 1553 data words are 16 bits long. Data words may be transmitted by either the BC or an RT. Other than designating the first bit transmitted as the MSB, MIL-STD-1553 does not define the bit definitions and formats of data words. These are typically defined by system-level ICDs (Interface Control Documents).
- Status Word
Status words are transmitted by Remote Terminals. The first five bits provide the RT’s address and provide acknowledgement to the bus controller. Other status word bits convey the status of the RT or the connected sub-system.
- Cards
There are multiple types of cards: multi-function, single-function, and dual-function. Multi-function cards can support the three functions simultaneously. This includes managing a bus and emulating one or more RTs at the same time.
Single-function cards can also support the three functions, but not simultaneously. Dual-function cards can support BC + Monitor or RT + Monitor modes simultaneously.
