BCRTM-26
6.1.3 Mode Code Descriptor Definition
Mode codes are handled similarly to subaddress
transactions. Both use the four-word descriptors residing in
the RT descriptor space to allow the host to program their
operational mode. Corresponding to each mode code is a
descriptor (see figure 9a). Of the 32 address combinations
for mode codes in MIL-STD-1553B, some are clearly
defined functions while others are reserved for future use.
Sixteen descriptors are used for mode code operations with
each descriptor handling two mode codes: one mode code
with an associated data word and one mode code without
an associated data word. All mode codes can be handled in
accordance with MIL-STD-1553B. The function of the first
word of the Mode Code Descriptor is similar to that of the
Subaddress Descriptor and is defined below. The remaining
three words serve the same purpose as in the
Subaddress Descriptor.
Control Word
Bit
Number Description
BIT 15 Interrupt on Reception of Mode Code (without Data Word).
BIT 14 Illegalize Broadcast Mode Code (without Data Word).
BIT 13 Illegalize Mode Code (without Data Word).
BIT 12 Reserved.
BIT 11 Illegalize Broadcast Mode Code (with Data Word).
BIT 10 Illegalize Transmit Mode Code (with Data Word).
BIT 9 Illegalize Receive Mode Code (with Data Word).
BIT 8 Interrupt on Reception of Mode Code (with Data Word).
BIT 7 Interrupt if Index = 0.
BITs 6-0 Index. Functionally equivalent to the index described in the Subaddress Descriptor. It applies to mode codes with
data words only.
Figure 9a. (RT) Mode Code Descriptor Space
RTDSSA + 320
MODE CODE
MODE CODE
MODE CODE (RTDSSA) + 256
STARTING ADDRESS
DESCRIPTOR SPACE
REMOTE TERMINAL
#’S 15 & 31
#’S 2 & 18
#’S 1 & 17
#’S 0 & 16
MODE CODE
Note:
Mode code descriptor blocks are also provided for reserved mode
codes but have no associated predefined BCRTM operation.
15 14 13 12 11 10 9 8 7 6 0
MESSAGE STATUS LIST POINTER
DATA LIST POINTER
RESERVED
INDEX
ILLEGALIZE BROADCAST MODECODE
(WITHOUT DATA WORD)
INTERRUPT ON RECEPTION OF MODE CODE
(WITHOUT DATA WORD)
ILLEGALIZE MODE CODE
(WITHOUT DATA WORD)
RESERVED
ILLEGALIZE BROADCAST MODECODE
(WITH DATA WORD)
ILLEGALIZE RECEIVE MODE CODE
(WITH DATA WORD)
INTERRUPT ON RECEPTION OF MODE CODE
(WITH DATA WORD)
INTERRUPT IF INDEX = 0
ILLEGALIZE TRANSMIT MODE CODE
(WITH DATA WORD)
Figure 9b. (RT) Mode Code Descriptor