5.4 Counters
The programmers of the MELSEC System Q also have internal counters that you can use for
programming counting operations.
Counters count signal pulses that are applied to their inputs by the program. The counter out
-
put is switched on when the current counter value reaches the setpoint value defined by the
program.Like timers, counter outputs can also be polled as often as you like in the program.
A counter is represented by four elements:
–
Set value (
CValue
)
–
Actual value(
CN
)
–
Counter coil (
CCoil, CC
)
–
Counter contact (
CS
)
Example of a program using a counter:
Whenever input X1 is switched on the value of counter C0 is incremented by 1. Output Y10 is
set when X1 has been switched on and off ten times (the counter setpoint is K10).
The signal sequence generated by this program is as follows:
The following table shows the key features of these counters.
MELSEC System Q Beginners Manual 5 – 9
Devices in Detail Counters
Ladder Diagram
MELSEC Instruction List
LD X1
OUT C0
K10
LD C0
OUT Y10
LD X0
RST C0
IEC
Instruction List
LD X1
COUNTER_M CC0, 10
LD CS0
ST Y10
LD X0
R CN0
As variable for the CCoil input of the
COUNTER_M instruction the device address of
the counter is specified (in this example CC0).
Once the counter value has reached the set
-
point value any additional pulses on input X1
no longer have any effect on the counter.
First the counter is reset with input X0 and a
RST instruction. This resets the counter value
to 0 and switches off the counter output.
0
1
2
3
4
5
6
7
8
9
10
X0
X1
Y10
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