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2.8 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 ( Page 77, Section 2.8.1)
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 ( Page 80, Section 2.8.2)
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 I/O modules at execution of an instruction. Therefore, data is input faster than
when it is input in refresh mode. Processing time required for each instruction, however, takes longer. The
following table lists the availability of the refresh mode and the direct mode for each input and output.
*1 The module must be mounted on the AnS/A series compatible extension base unit (QA1S5B, QA1S6B, QA6B,
QA6ADP+A5B/A6B, or QA1S6ADP+A1S5B/A1S6B). (The CPU module whose serial number (first five digits) is
"13102" or later must be used. However, the QnUDPV cannot be used.)
Item Refresh mode direct mode
Input/output modules
Available Available
Input/output of intelligent function modules
Input/output of MELSEC-I/O LINK Remote I/O System Master
Module (AJ51T64/A1SJ51T64)
*1
Remote input/output in CC-Link IE, CC-Link IE Field Network Basic,
MELSECNET/H, or CC-Link
Available Not available
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