Mitsubishi Electronics FX3G User Manual

FX

3S

/FX

3G

/FX

3GC

/FX

3U

/FX

3UC

 Series

Programming Manual - Basic & Applied Instruction Edition

4 Devices in Detail

The valid set range of 32-bit binary bi-directional counters is from 

−2,147,483,648 to +2,147,483,647 (decimal

constant). The counting direction (up or down) is specified by special auxiliary relays M8200 to M8234.
• When M8UUU is driven for CUUU, a counter executes down-counting. When M8UUU is not driven, a counter 

executes up-counting. (Refer to the previous page.)

• The set value (positive or negative) can be specified by a constant (K) or the contents of data registers (D).

When data registers are used, 32-bit data composed of paired serial devices are treated as set values.
For example, when D0 is specified, D1 and D0 provide a 32-bit set value.

• When the coil C200 is driven by the counting input X014, a counter starts up-counting or down-counting.

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 regardless of the operation of the output contact. When a counter 

executes up-counting from "+2,147,483,647", the counter value becomes "

−2,147,483,648". In the same way, 

when a counter executes down-counting from "

−2,147,483,648", the counter value becomes "+2,147,483,647". 

(This type of counter is called ring counter.)

• When the reset input X013 turns ON and then RST instruction is executed, the current value of the counter is reset 

to "0" and the output contact returns.

• For latched (battery backed) type counters, the current value, output contact operation and reset status are backed 

up against power failure. 
In FX

3U

/FX

3UC

 PLCs, latched type counters are backed up by the battery built into the PLC.

In FX

3S

/FX

3G

/FX

3GC

 PLCs, latched type counters are backed up by the EEPROM built into the PLC.

→ For details on backup methods against power failure, refer to Section 2.6.

• A 32-bit counter can be used as a 32-bit data register. 32-bit counters cannot be handled as target devices in 16-bit 

applied instructions.

• If data beyond the set value is written to the current value register by DMOV instruction, etc., the counter continues 

counting and the contact does not change when the next counting input is received.

1) Specification by constant (K) 

2) Indirect specification (D)

X013

RST

C200

X014

C200

C200

Y001

K-5

Set value (constant)

It can be specified

indirectly also.

X012

M8200

X012

X013

X014

Current

value

Y001

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

been already

activated.

−7−

6−5

−4−3

0

X003

C 0

K100

Constant (decimal constant): 1 to 32767

100 counts

X001

FNC 12

MOV

K100

D  5

X003

C 0

D 5

D5 = 100
100 counts

Counts to the indirectly specified value of the defined data
register, previously set by a digital switch.
Note that the set value of a latched (battery backed) type 
register is not held correctly sometimes when the battery 
voltage becomes low.