138
Exchanging Data with the CPU Unit Section 3-3
Sequence Table block (Block Model 302), the Step Ladder Program block
(Block Model 301) and the ITEM Setting blocks (Block Models 171 and 172).
Note When ITEM014 (run/stop command) of the System Common block is set to 0,
the Loop Controller will not start to run as it is even if the CPU Unit operation
mode is set to RUN or MONITOR. To resume running of the Loop Controller,
ITEM014 (run/stop command) of the System Common block must be set to
either 1 (hot start) or 2 (cold start).
Example To indicate switching to the preset MV value of PID control or MV hold in the
System Common block
Likewise, to forcibly set the MV (manipulated variable) to a specific value from
the Advanced PID block when the CPU Unit is in the PROGRAM mode, input
ITEM013 (PROGRAM mode) of the System Common block as the run status
of the CPU Unit, and set the preset MV switch (ITEM080) or the MV hold
switch (ITEM082) of the Advanced PID block to ON.
Run status of Loop
Controller
The run status of the Loop Controller is reflected at all times in A35800 to
A35815 in the CPU Unit. For this reason, the required processing can be exe-
cuted by the Step Ladder Program of the CPU Unit taking this run status as
the input conditions.
Note On the Loop Controller, the refresh timing of the words allocated in the Auxil-
iary Area of the CPU Unit is not the I/O refresh timing of the CPU Unit, but the
refresh timing of the 1 sec operation cycle (fixed) for LCB01 and LCB05. (The
refresh timing is the CPU Unit cycle time (each duplex refresh) for LCB05D.)
To perform processing
from the CPU Unit
according to the run
status of the Loop
Controller
So that the CPU Unit can perform specific processing (for example, changing
the analog output value to a specific value) according to the run status of the
Loop Controller, create a Step Ladder Program taking bits A35800 to A35815.
System Common
blocks
Sequence Table or
Step Ladder
Program block
System Common
blocks
013
ITEM Setting block
014
System Common
block
Sequence Table
or Step Ladder
Program block
Advanced PID
block
080/082
013
Loop Controller CPU Unit
Auxiliary Area
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