162
MC, MCR
Cautions when Using Nesting Architecture
(1) Nesting can be used up to 15 times (N0 to N14)
When using nesting, nests should be inserted from the lower to higher nesting number (N) with the MC instruction, and
from the higher to the lower order with the MCR instruction.
If this order is reversed, there will be no nesting architecture, and the CPU module will not be capable of performing
correct operations. For example, if nesting is designated in the order N1 to N0 by the MC instruction, and also
designated in the N1 to N0 order by the MCR instruction, the vertical bus will intersect and a correct master control
ladder will not be produced.
[Ladder as displayed in the GPP ladder mode] [Ladder as it actually operates]
(2) If the nesting architecture results in MCR instructions concentrated in one location, all master controls can be terminated
by use of just the lowest nesting number (N).
MC
N1
M15
MC N0M16
MCR
N0
N1
M15
N0M16
A
MCR
N1
MC
N1
M15
MC N0M16
MCR
N0
N1
M15
N0M16
A
B
MCR
N1
MC NO M15
MC N1
M16
MC N2M17
MCR
N2
MCR
N0
NO M15
N1M16
N2M17
X1
X2
X3
MCR
N1
MC NO M15
MC
N1
M16
MC
N2M17
MCR
N0
NOM15
N1M16
N2M17
X1
X2
X3
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