Chapter 16 PLC Function Applications│CP2000
16-20
ORB command: A configuration in which one block is in parallel with one device or block.
In the case of ANB and ORB operations, if a number of blocks are connected, they should be
combined to form a block or network from the top down or from left to right.
MPS, MRD, MPP commands: Branching point memory for multiple outputs, enabling multiple,
different outputs. The MPS command begins at a branching point, where the so-called branching
point refers to the intersection of horizontal and vertical lines. We have to rely on the contact status
along a single vertical line to determine whether the next contact can give a memory command.
While each contact is basically able to give memory commands, in view of convenience and the
PLC's capacity restrictions, this can be omitted from some places when converting a ladder diagram.
The structure of the ladder diagram can be used to judge what kinds of contact memory commands
are used.
MPS can be distinguished by use of the "┬" symbol; this command can be used consecutively
for up to 8 times. The MRD command is read from branching point memory; because logic states
along any one vertical line must be the same, in order to continue analysis of other ladder diagrams,
the original contact status must be read.
MRD can be distinguished by use of the "├" symbol. The MPP command is read from the
starting state of the uppermost branching point, and it is read from the stack (pop); because it is the
final command along a vertical line, it indicates that the state of the vertical line can be concluded.
MPP can be distinguished by use of the "└" symbol. Although there should basically be no errors
when using the foregoing analytical approach, the compiling program may sometimes omit identical
state output, as shown in the following figure:
(
)
(
)
(
)
(
)
(
)
(
)
(
)
MPS
MPP
MRD
To Next Page
Loading...
