Mitsubishi MELSEC Q Series Programming Manual page 903

(7) Interlock when using the multiple CPU high-speed transmission dedicated instruction
(a) Special relays SM796 to SM799 (maximum number of used blocks for multiple CPU
high-speed transmission dedicated instruction setting) can be used as an interlock for
the multiple CPU high-speed transmission dedicated instruction.
When executing the multiple CPU high-speed transmission dedicated instructions
concurrently, use SM796 to SM799 as an interlock for the instructions.
When using special relays SM796 to SM799, set the maximum number of blocks
for the instruction used for each CPU to special registers SD796 to SD799. (For
example, when the maximum number of blocks for the multiple CPU high-speed
transmission dedicated instruction to be executed to CPU No.3 is 5, set 5 to
SD798.)
When the multiple CPU high speed transmission area becomes equal to or less
than the number of blocks set at SD796 to SD799, the corresponding special
relay (SM796 to SM799) turns on.
CPU No.1
SM
Execution
797
command
DP.DDWR
Turns on when the number of empty blocks
is less than the number of blocks used for
the DP.DDWR instruction.
(The DP.DDWR instruction is not executed.)
CPU No.1
SM
Execution
797
command
DP.DDWR
Turns off as empty blocks by the number of blocks
used for the DP.DDWR instruction became available
(The DP.DDWR instruction can be written.)
Multiple CPU high speed transmission area Multiple CPU high speed transmission area
H3E1
Number of request blocks:4
Empty area of the request blocks in send area (1 2) has been increased.
Multiple CPU high speed transmission area Multiple CPU high speed transmission area
H3E1
Number of request blocks:4
The request from the DP.DDWR instruction can be written.
Send area Receive area
(1 2) (1 2)
During use
Number of empty blocks:
2
Lnsufficient for writing a request from
the DP.DDWR instruction.
Send area Receive area
(1 2) (1 2)
During use
Number of empty blocks:
8
7
10
7
7
7
7
CPU No.2
7
7
CPU No.2
10-7