Omron SYSMAC CS Series Operation Manual page 163

Description of Operation
1,2,3...
Monitoring the LCB
load rate at the trial
operation stage
1,2,3...
Though errors caused by PID and other operations do not occur when the
LCB load rate exceeds 80%, use the Loop Controller at a LCB load rate of
80% or lower as there is possibility that the LCB load rate will temporarily
increase due to fluctuations in the overhead time of FINS command communi-
cations and internal processing.
Monitor the maximum LCB load rate from the CX-Process Tool system opera-
tion verification function. (Select Operation - Validation from the Execute
Menu and check the value of ITEM 048 (maximum LCB load rate). The value
that is given will be the largest LCB load rate since operation was begun.
If the LCB load rate exceeds 1005, operation will continue and the operation
cycles will be exceeded as shown below. There will be errors, however, in PID
calculations.
Block F
Block A
Actual operation time
Set operation cycle
Take the following steps if the LCB load rate exceeds 80%.
1. If there are any blocks for which a longer operation cycle can be set without
affecting the applications, increase their operation cycles.
2. If the LCB load rate still exceeds 80% and the operation cycles cannot be
increased any further, add on a CPU Unit.
3. If a CPU Unit cannot be added, add on a Loop Control Unit (up to three
Loop Control Units can be mounted on a single PLC) and distribute pro-
cessing between the mounted Units.
At the trial operation stage, monitor which value the LCB load rate actually
reaches at the preset operation cycle(s) on CX-Process Tool.
Follow the procedure below to monitor the LCB load rate.
1. Download the function block data to the Loop Controller.
2. Start running of the Loop Controller using CX-Process Tool or by turning
the PLC power OFF then back ON again.
3. Establish the connection to CX-Process Tool, and select Operation - Run
monitor status from the Execute menu.
The following LCB load rates (current LCB load rate and maximum LCB
load rate) are displayed in the Run monitor status screen:
Each of the current LCB load rates and maximum LCB load rates for the
system common operation cycle and each of the 0.1 s/0.2 s/0.5 s/1 s/2 s
operation cycle groups
If the maximum LCB load rate of a certain operation cycle group exceeds
80%, change the operation cycle of function blocks among function blocks
within that group, for which an increased operation cycle will not affect the
application, to a longer operation cycle (group).
If it is estimated that an operation cycle longer than this cannot be set when
the LCB load rate exceeds 80%, add on a CPU Unit or a Loop Control Unit
(up to three Loop Control Units can be mounted on a single PLC) and dis-
tribute processing between the mounted Units.
Block A
Actual operation time
Set operation cycle
Set cycle exceeded.
Section 3-2
Time
Block F
Set cycle exceeded.
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