Omron SYSMAC CS1W-LCB01 Operation Manual page 206

Fail-safe Countermeasure Guidelines
Fail-safe
countermeasures for
adapting to stoppage of
the Loop Controller when
the CPU Unit is in the RUN
or MONITOR mode
(CS1W-LCB01/05 or CS1D-
CPU@@P in simplex
mode)
Fail-safe
countermeasures for
adapting to stoppage of
the Loop Controller when
the CPU Unit is in the
PROGRAM mode
1,2,3...
172
Implement the following fail-safe measures to hold analog outputs or contact
outputs at specific values (for example, maximum value or minimum value)
when the Loop Controller has stopped running.
To hold analog outputs or contact outputs at specific values when the Loop
Controller (CS1W-LCB01/05) or Process-control CPU Unit (CS1D-CPU@@P)
in simplex mode has stopped running, create a Step Ladder Program on the
CPU Unit so that each of the bits on the Analog Output Unit or Contact Output
Unit are set to a specific value taking the N.C. condition of the Loop Controller
CPU Unit Running flag (A35801) as the input condition.
Loop Controller running
A35811
Analog output operation
When an Analog Output Unit (for example, CS1W-MAD44) is used in regular
operation (that is, operation without a Loop Controller), the Analog Output
Conversion Enable flag turns OFF and analog output values are output
according to the setting of the output hold function when the CPU Unit
changes from the RUN or MONITOR mode to the PROGRAM mode.
However, when analog values are output via the Analog Output Unit by the
Loop Controller, the Analog Output Conversion Enable flag is forcibly turned
ON by the Loop Controller even if the CPU Unit is in the PROGRAM mode,
and the output hold function does not work.
The analog output setting values are refreshed and then output.
Contact output operation
Normally, the Contact Output Unit also turns OFF when the CPU Unit
changes from the RUN or MONITOR mode to the PROGRAM mode. (The I/O
Memory Hold flag is used to hold output values.)
However, when contact values are output via the Contact Output Unit by the
Loop Controller, contact outputs are refreshed and then output if the CPU Unit
is in the PROGRAM mode.
Implement the following fail-safe measures to hold analog outputs or contact
outputs at specific values (for example, maximum value or minimum value)
when the Loop Controller has stopped running even if the CPU Unit is in the
PROGRAM mode.
1. When the user uses SCADA software or CX-Process Tool to stop running
of the Loop Controller when the CPU Unit is in the PROGRAM mode:
Before the Loop Controller is made to stop running, switch Control blocks
such as PID blocks to Manual, and use or CX-Process Tool to execute set-
ting so that the MV becomes the required value.
2. To set ITEM014 (run/stop command) of the System Common block to 0
(stop) by the ITEM Setting blocks on the Loop Controller:
Before writing to the ITEM Setting blocks, switch Control blocks such as
PID blocks to Manual, and create a sequence so that the MV becomes the
required value beforehand using the Step Ladder Program block.
Note 1. When the Loop Controller stops running due to a malfunction of the Loop
Controller itself when the CPU Unit is in the PROGRAM mode, analog out-
put or contact output cannot be held at specific values (for example, max-
Processing at stoppage of Loop
Controller
• Analog output setting value on
Analog Output Unit changed by
MOV instruction
• Contact state of Contact Output
Unit changed by SET/RSET
instruction
Section 3-6