YOKOGAWA FA-M3V e-RT3 Plus, Hardware Manual

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A2-28
IM 34M06C11-01E
(4) Functional Description
- Pulse-capture Function
The pulse-capture function is designed to reliably catch input pulses shorter than the
scan time.
As the CPU module usually reads the data of I/O modules during I/O refresh cycle,
when a normal input module is used, the CPU may fail to read input pulses shorter
than the scan time. The F3XH04-3N module provides a pulse capture function,
which can, once it detects pulses longer than 50µs, hold the data until the next
timing for data reading so that such pulses can be reliably captured by the the CPU
during I/O refreshing. However, the F3XH04-3N module cannot catch input pulses
shorter than 50µs.
The timing diagram of this function is shown below.
Pulse capture
CPU processing Refreshing Refreshing Refreshing
Input
Internal
buffer
ꞏ Shorter than
50

s
ꞏ Unreadable
Load into internal buffer I/O read enabled
ꞏ Shorter than
50

s
ꞏ Unreadable
1 scan 1 scan
ꞏ Longer than
50

s
ꞏ Readable
FA020508.VSD
Figure A2.11 Behavior when Pulses Shorter than the Scan Time are Inputted
When a pulse longer than the scan time is inputted, the input is regarded as having
been on only for the duration of one scan time.
Refreshing
1 scan
Internal buffer
1 scan 1 scan
Refreshing Refreshing Refreshing
Read as ON Read as OFF
Pulse capture
CPU processing
Input
Internal
buffer
FA020509.VSD
Figure A2.12 Behavior when Pulses Longer than the Scan Time are Inputted