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10 Use of High-speed Counters
90
FX
3S
 Series Programmable Controllers
User's Manual - Hardware Edition
10.5 Handling of High-speed Counters
• C235 is set to the up-count or down-count mode through interruption by the count input X000.
• When the current value increases from -6 to -5, the output contact is set, and when the value decreases 
from -5 to -6, it is reset.
• The current value increases and decreases regardless of the operation of the output contact. However, 
when the counter’s value increments from 2,147,483,647, it changes to -2,147,483,648. In the same 
manner, when it decrements from -2,147,483,648, it changes to 2,147,483,647. (This type of counter is 
called a ring counter.)
• When RST instruction is executed after the reset input X011 turns on, the current counter's value resets to 
0, and the output contact is restored.
• The current value, output contact operation and reset status of counters are backed up (kept) even if the 
power is turned off.
10.5.2 1-phase 2-count input
These counters are 32-bit up-count/down-count binary counters.
The operations of the output contact according to the current value are the same as those of the above-
mentioned 1-phase 1-count input high-speed counters.
Examples of program
1) For C246
• While X012 is on, C246 increments the value when the 
input terminal X000 switches from OFF to ON and 
decrements the value when the input terminal X001 
switches from OFF to ON.
• The down-count/up-count operations of C246 to C250 can 
be monitored through the ON/OFF operations of M8246 to 
M8250.
ON : Down-counting
OFF: Up-counting
2) For C249
• While X012 is on, C249 starts counting immediately when 
the input terminal X006 turns on. The up-counting input 
terminal is X000, and the down-counting input terminal is 
X001.
• C249 can be reset on the sequence by X011. For C249, 
X002 is allocated as reset input. When X002 turns on, C249 
is immediately reset.
• The down-count/up-count operations of C246 to C250 can 
be monitored through the ON/OFF operations of M8246 to 
M8250.
ON : Down-counting
OFF: Up-counting
X000
Main unit
Up-counting
input
X001
Down-counting
input
The setting is (D3, D2)
X011
X012
C246
D2 (D3)
RST
C246
X011
X012
C249
K1234
RST
C249
X000
Main unit
Up-counting
input
X001
Down-counting
input
X002
X006
External reset
input
External start
input