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FX Series Programmable Controllers Devices in Detail 4
4-29
4.11.6 A/B Phase Counters (C252 to C255)
With these counters only the input identified in the previous high speed counter tables can be
used for counting. The counting performed by these devices is independent of the program
cycle (scan) time. Depending on the counter used, start, reset and other associated inputs are
automatically allocated.
The A phase, B phase input signal not only
provide the counted signals but their
relationship to each other will also dictate the
counted direction.
While the wave form of the A phase is in the
ON state and...
the B phase moves from OFF to ON the
counter will be counting up.
However, if...
the B phase moves from ON to OFF the
counter will be in a down configuration.
One count is registered after both A and B
phase inputs have been given and released in
the correct order.
C251 counts the ON/OFF events of input X0
(the A phase input) and input X1 (the B phase
input) while X11 is ON.
C255 starts counting immediately when X7 is
turned ON while X13 is ON. The counting
inputs are X3 (A phase) and X4 (B phase).
C255 is reset when X5 is turned ON. It can
also be reset with X12 in the sequence.
Device specification:
• A maximum of 2 points - 2 phase, 32bit, up/down counters can be used. The operation of
the output contact in relation to the counted data is the same as standard 32bit counters
described in section 4.11.
Setting range:
• -2,147,483,648 to +2,147,483,647
Direction setting:
• Check the corresponding special relay M8✰✰✰ to determine if the counter is counting
up or down.
A-phase
B-phase
A-phase
B-phase
Up-count
Down-count
X11
K1234
C251RST
X10
X13
D0
C255RST
X12
C251
C255