Hitachi HSC-2100 Hardware Manual page 116

(e) LED indication
• Pulse input indication LED:
Comes on and goes out in synchronism with 1-phase or 2-phase pulse counting.
• Comparison result indication LED:
Is lit in synchronism with comparison output.
The timing of comparison output and LED indication differs depending on models of
counter modules:
• In the case of model LWC400:
Every time the content of an internal register used for comparison output is updated
with a new value, comparison output is performed automatically, and immediately, to
output the new content of that register, regardless of whether a pulse input is made or
not. For example, when a new data value is set in the comparison data register, it is
automatically output by comparison output immediately and the comparison result
indication LED is lit in synchronism with that output.
• In the case of models LWC401 and LWC402:
Even if the content of an internal register used for comparison output is updated with
a new value, comparison output is not automatically performed to output the new
content of that register until a pulse input is made. For example, when a new data
value is set in the comparison data register, it is not automatically output by
comparison output. The new data value will be output later when a pulse input is
made. In synchronism with that output, the comparison result indication LED will
be lit.
5 MAKING USE OF MODULES
5-15