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FX3G/FX3U/FX3UC 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 FX3UC 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.
• The current value increases or decreases without regard to the operation of the output contact. When a counter
executes up-count from "+2,147,483,647", the counter value becomes "−2,147,483,648". In the same way, when a
counter executes down-count from "−2,147,483,648", the counter value becomes "+2,147,483,647". (This type of
counter is called a ring counter.)
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