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MELSEC-Q
16 COMMUNICATION BETWEEN CPU MODULES IN MULTIPLE PLC
SYSTEM
(2) Precautions
(a) The following values are set in the CPU module's first I/O number with the
FROM instruction, the S. TO instruction and instructions that use U
\G .
PLC No. PLC No.1 PLC No.2 PLC No.3 PLC No.4
Value set in the first I/O number 3E0
H
3E1
H
3E2
H
3E3
H
(b) Do not perform writing as reading in the system area or automatic refresh
area for the CPU shared memory (see Section 16.4).
(c) An error will not occur when CPUs accessed with the FROM instruction, the
S. TO instruction and instructions that use U
\G are reset.
However, access execution flag (SM390) will remain OFF when instruction
execution has been completed.
(d) Establish an interlock to prevent simultaneous access during interactive
data communication with the FROM instruction, the S. TO instruction and
instructions that use U
\G .
There are cases where old data and new data will be mixed together if
simultaneous access is carried out.
(e) The instruction that uses the S. TO instruction/U
\G cannot be used to
write data to the CPU shared memory of other PLCs.
"SP. UNIT ERROR (error code: 2115)" occurs if data is written to the CPU
shared memory of other PLCs with the instruction that uses U
\G .
"SP. UNIT ERROR (error code: 2117)" occurs if data is written to the CPU
shared memory of other PLCs with the instruction that uses the S. TO
instruction.
(f) "SP. UNIT ERROR (error code: 2114)" also occurs if data is written into the
CPU shared memory of the host PLC with instructions that use U
\G .
(g) "SP. UNIT ERROR (error code: 2114)" occurs if data is read from the CPU
shared memory of the host PLC with the FROM instruction and instructions
that use U
\G .
(h) "SP. UNIT ERROR (error code: 2110)" also occurs if access is attempted
on a non-mounted PLC with instructions that use U
\G .
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