<8. Detailed Description>
● Checking Specification of Digital Output Module (NFDV551, NFDV557,
NFDV561)
Digital output modules can also be used for pulse width output but the minimum
output pulse width and increment is the same as the scan cycle.
• Minimum output pulse width
The minimum ON/OFF interval for digital output is the same as the scan cycle.
Therefore, when using digital output module, the minimum output pulse width
and increment are the same as the scan cycle of the FCN-500 or FCN-RTU.
The example below shows an FCN outputting ON/OFF signals at each scan
cycle of 100 ms.
As the FCN cannot output ON/OFF signals at intervals shorter than the scan
cycle, the minimum output pulse width is the same as the scan cycle (i.e. 100
ms).
For the same reason, the output increment is also the same as the scan cycle
(i.e. 100 ms).
100ms 100ms 100ms 100ms 100ms 100ms 100ms
Verify that this specification matches the specification of equipment used.
To shorten the minimum output pulse width, shorten the scan cycle.
SEE ALSO
For details on how to decide the scan cycle, see Section 2.2.4, “Determining FCN/FCJ Scan Cycle.”
• Defining operation upon CPU failure
A digital output module can be used for pulse width output, but unlike a pulse
width output module, its operation remains unaltered upon detection of a CPU
failure.
SEE ALSO
For details on operation upon CPU failure, see Section 8.1.2, “Checking Operation Specification of
Analog/Digital Output”
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