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112
FX
3G
/FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.7 High Speed Counter [C] (FX3U/FX3UC PLC)
Restriction to overlap input numbers
• Inputs X000 to X007 are used for high speed counters, input interrupt, pulse catch, SPD/ZRN/DSZR/DVIT
instructions and general-purpose inputs. When assigning functions, there should be no overlap between
those input terminals.
For example, when C251 is used, X000 and X001 are occupied. As a result, "C235, C236, C241, C244,
C246, C247, C249, C252 and C254", "input interrupt pointers I000 and I101", "pulse catch contacts M8170
and M8171" and "SPD, ZRN, DSZR and DVIT instructions using X000 and/or X001" cannot be used.
• Since the FX
3U
-4HSX-ADP and FX
3UC
PLC main unit share the same assigned input terminal numbers,
only one of them may be used in operation. If both input terminals are used, intended operation is not
enabled because the inputs of the FX
3U
-4HSX-ADP and PLC main unit operate in an "OR" relationship.
4.7.3
Handling of high speed counters
1. 1-phase 1-count input
• C235 counts "OFF
→
ON" of the input X000 while X012
is ON.
• When X011 turns ON and then RST instruction is
executed, C235 is reset.
• The counting direction of the counters C235 to C245 is
switched to down-count or up-count when M8235 to
M8245 turns ON or OFF.
• C244 immediately starts counting when the input X006
turns ON while X012 is ON. The counting input is X000.
In this example, the set value is indirectly specified by
the contents of data registers (D1 and D0).
• A high speed counter can be reset using X011 in a
sequence as shown in the figure, but C244 immediately
reset without any program when X001 is closed. So a
program with X011 is not necessary.
• The counting direction of the counters C235 to C245 is
switched to down-count or up-count when M8235 to
M8245 turns ON or OFF.
Operation example
The counter C235 shown above operates as follows:
When counting with input X000, C235 executes up-count or down-count as an interrupt.
• When the current value of a counter increases from "
−
6" to "
−
5", the output contact is set. When the
current value decreases from "
−
5" to "
−
6", the output contact is reset.
X010
M8235
Down/up count
X011
X012
C235
K-5
RST
C235
Reset
X010
M8244
Down/up count
X011
X012
C244
D0(D1)
RST
C244
Reset
Set value is (D1, D0)
X010
X011
X000
C235
Current
value
C235 output contact
Up counting
Down counting
Up counting
0
1
2
3
4
5
4
3
2
1
0
−
1
−
2
−
3
−
4
−
5
−
6
−
7
−
8
When output has
already been activated
−
7
−
6
−
5
−
4
−
3
0
X012
Reset input
Start input
Counting
input