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CHAPTER3 CPU MODULE OPERATION
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3.8 I/O Processing and Response Delay
3.8 I/O Processing and Response Delay
The CPU module performs I/O processing in the refresh mode.
Using the direct access input/output in a sequence program, however, allows the CPU module to perform
I/O processing in the direct mode at the time of each instruction execution.
This section describes these I/O processing modes of the CPU module and response delays.
(a) Refresh mode ( Section 3.8.1)
Refresh mode is a mode for the CPU module to access input/output modules and perform I/O processing
collectively before the start of sequence program operations.
(b) Direct mode ( Section 3.8.2)
Direct mode is a mode for the CPU module to access input/output modules and perform I/O processing at the
timing when each instruction is executed in a sequence program.
To access input/output modules in the direct mode, use the direct access input or direct access output in a
sequence program.
(1) Differences between refresh mode and direct mode
The direct mode directly accesses input/output modules at execution of an instruction. Therefore, data input is
faster than in refresh mode.
Processing time required for each instruction, however, is longer.
Table3.4 shows the availability of the refresh mode and the direct mode for each input and output.
*1: The module must be used with being mounted on the AnS/A series-compatible extension base unit (QA1S5 B, QA1S6 B,
QA1S6ADP+A1S5 B/A1S6 B, QA6 B, or QA6ADP+A5 B/A6 B). (The High Performance model QCPU only)
Table3.4 Availability of modes
Item Refresh mode direct mode
Input/output modules
Available Not available
Input/output of intelligent function modules
Input/output of the MELSEC-I/OLINK remote I/O system master module
(AJ51T64/A1SJ51T64)
*1
Remote input/output in CC-Link IE Controller Network, MELSECNET/H, or
CC-Link
Available Not available
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