Aim MIL-STD-1553 - Page 264

MIL-STD-1553 Reference Manual
250
Chapter 7 – Bus Controller Functions
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Expected Response Control for Command Word
Value
Constant
Description
0
API_BC_RSP_AUTOMATIC
Automatic Response Control
In this mode BC expects appropriate RT-
Response to the defined Transfer Type,
dependent on the MIL-STD 1553 protocol
type(s), which is (are) defined for the RT(‘s)
with the function ApiCmdDefMilbusProtocol
1
API_BC_RSP_NO_SW1_EXPECTED
No Status Word 1 expected (Note: for RT-
RT transfer type Status Word 1 represents
the status response for the Transmit
Command word)
2
API_BC_RSP_NO_SW2_EXPECTED
No Status Word 2 expected (RT-RT
transfer type only, Note: for RT-RT transfer
type Status Word 2 represents the status
response for the Receive Command word)
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Three different Gap Modes are available which are described after the following table:
Value
Constant
Description
0
API_BC_GAP_MODE_DELAY
Delay mode / Transfer Wait Time mode
1
API_BC_GAP_MODE_STANDARD
Standard Gap Mode
2
API_BC_GAP_MODE_FAST
Fast Intermessage Gap Mode
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In this mode ‘gap’ (14bit) specifies the time from the start of a transfer to the start of the
following transfer in µs.
Note: If the specified time is shorter than the actual time needed for transfer
transmission, ‘gap’ is ignored and the Bus Controller automatically
generates a minimum intermessage gap of app. 11µs.
This gap mode guarantees deterministic framing independent from RT response times
and provides excellent repeatability of timed bus events.
The nominal Transfer Wait Time is calculated as:
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= ‘gap’ * 1s
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In Standard Gap Mode ‘gap’ (14bit) specifies the wait gap between the end of the current
transfer and start of the following transmitted Command Word. The nominal
Intermessage Gap Time is calculated as:
T
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= ‘gap’ * 1s
Note: The idle time of the physical bus is 2.0µs less than this time due to the
gap measurement definition of MIL-STD-1553B.
Note: The minimum Intermessage gap time achieved using the Standard Gap
Mode is equal to the minimum gap time achieved in the Transfer Wait
Time Mode.