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MELSEC-Q
15 ALLOCATING MULTIPLE PLC SYSTEM I/O NUMBERS
15 ALLOCATING MULTIPLE PLC SYSTEM I/O NUMBERS
15.1 Concept behind Allocating I/O Numbers
Multiple PLC systems possess I/O numbers to enable interactive transmission
between the CPU modules and the I/O modules and intelligent function modules, and
I/O numbers to enable interactive transmission between the CPU modules.
15.1.1 I/O modules and intelligent function module I/O numbers
The difference with single CPU systems is the 00
H
position (slot) of the I/O number
with multiple PLC systems.
However, the concept behind the sequence for allocating I/O numbers, the I/O
numbers for each slot, and the I/O numbers for empty slots is the same for both types
of system.
See Chapter 5 (Allocating I/O Numbers) for details on the concept behind the
sequence for allocating I/O numbers, the I/O numbers for each slot, and the I/O
numbers for empty slots.
(1) "00
H
" position for I/O numbers
(a) The number of slots set with the PLC parameters' multiple PLC settings are
occupied by the CPU modules on the multiple PLC system.
(b) The I/O modules and intelligent function modules are mounted from the
right of the slots occupied by the CPU modules.
(c) I/O number of a system without PC CPU module
The I/O number for the I/O modules and intelligent function modules
mounted from the right of the slots occupied by the CPU modules is set as
"00H" and consecutive numbers are then allocated sequentially to the right.
1) Example: Two modules are mounted
01234
Power supply
567
I/O number : 00
Empty
Power supply
QCPU
QCPU
QCPU
(d) Input/output number of a system with PC CPU module
The PC CPU module occupies two slots. The one on the right side among
the two slots is handled as an empty slot. (16 empty points are occupied
with default setting.) Therefore the I/O number of the slot on the right side
of the PC CPU module is "10H." (Set the empty slot at zero point using I/O
allocation of PLC Parameters dialog box, to assign "00H" to the first I/O
number.)
0123
Power supply
Empty slot (00H to 0FH: occupied)
CPU count (4)
QCPU
QCPU
QCPU
PC CPU module
REMARK
• If the number of CPU modules mounted on the main base unit is smaller than the
number set at the "Multiple PLC setting" of “(PLC) Parameter" dialog box, the
slot(s) on the right of the actually mounted CPU modules is (are) set as "CPU
(Empty).
• The I/O number for the multiple PLC system can be confirmed with the system
monitor.
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