3.1 Basic Functionality
Scans
3-37
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 service
clears the input registers.
If the high-speed scan time setting is set to 0.250 ms or 0.125 ms, the scan at which the input reg-
isters are cleared will differ for the MP2000-series Optional Module and the 218IFD and SVC32
Function Modules that are built into the CPU Unit.
In the following example, an input error occurs simultaneously on the MP2000-series Optional
Module and the 218IFD and 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 and SVC32 Function Modules 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 Modules
(218IFD and SVC32)
in the CPU Unit
MP2000
Optional Module
Service scan on MP2000-series Optional Module
immediately after the specified number of scans
Service scan on Function Modules in the CPU Unit
immediately after the specified number of scans
Input registers in the
Function Modules in the
CPU Unit are cleared.
The input registers in the MP2000
Optional Module are cleared.
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