3.1 Basic Functionality
3.1.4 Scans
3-34
3.
Set values in the High-speed Input and Low-speed Input Boxes in the Keep Latest
Value Group.
4.
Click the OK Button.
The settings will be saved and the Environment Setting Dialog Box will close.
The Keep Latest Value setting specifies the number of scans to process before the I/O ser-
vice clears the input registers.
If the high-speed scan time setting is set to 0.250, the scan at which the input registers are
cleared will differ for the MP2000-series Optional Module and the 218IFD, SVC, or SVC32
Function Module that is built into the CPU Unit.
In the following example, an input error occurs simultaneously on the MP2000-series
Optional Module and the 218IFD, SVC, SVC32 Function Modules in the CPU Unit when the
high-speed scan setting is set to 0.250 ms and the Keep Latest Value setting is set to 5
scans.
The input registers in the 218IFD, SVC, or SVC32 Function Module built into the CPU Unit are
cleared on the sixth scan that immediately follows the specified number of scans, whereas on
the MP2000-series Optional Module, the input registers are cleared on the seventh service
scan that immediately follows the specified number of scans.
0.250 ms
0.5 ms
Input error
Keep Latest Value setting = 5 scans for high-speed scan
High-speed scan
Function Module
(218IFD, SVC, or SVC32)
in the CPU Module
MP2000
Optional Module
Service scan on MP2000-series Optional Module
immediately after the specied number of scans
Service scan on Function Modules in the CPU Module
immediately after the specied number of scans
Input registers in the
Function Module in the
CPU Module are cleared.
The input registers in the MP2000
Optional Module are cleared.
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