Omron CJ1G-CPU series, Programming Manual

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Cycle Time/High-speed Processing Section 6-1
6-1-6 I/O Refreshing Methods
There are three ways that the CS/CJ-series CPU Units can refresh data with
Basic I/O Units and Special I/O Units: Cyclic refreshing, immediate refreshing,
and execution of IORF(097).
1. Cyclic Refreshing
I/O refreshing is performed after all of the instructions in executable tasks
have been executed. (The PLC Setup can be set to disable cyclic refreshing
of individual Special I/O Units.)
2. Immediate Refreshing
When an address in the I/O Area is specified as an operand in the immediate-
refreshing variation of an instruction, that operand data will be refreshed when
the instruction is executed. Immediate-refreshing instructions can refresh data
allocated to Basic I/O Units.
Immediate refreshing is also possible for the built-in I/O on CJ1M CPU Units.
Note 1. When the instruction contains a bit operand, the entire word containing
that bit will be refreshed. When the instruction contains a word operand,
that word will be refreshed.
2. Input and source data will be refreshed just before execution of the instruc-
tion. Output and destination data will be refreshed just after execution of
the instruction.
3. The execution times for immediate-refreshing variations are longer than
the regular variations of instructions, so the cycle time will be longer. Refer
to 10-5 Instruction Execution Times and Number of Steps in the Operation
Manual for details.
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I/O refreshing
Actual I/O data
Task
Task
Task
Immediate refreshing
Actual I/O data
CIO 0001
CIO 0002
CIO 0003
CIO 0004