Mitsubishi Electric MELSEC FX3U Programming Manual page 107

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2. General type and latched (battery backed) type 32-bit bi-directional counters
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 M8
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.
X012
X013
X014
C200
• 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 /FX
3U 3UC
In FX PLCs, latched type counters are backed up by the EEPROM built into the PLC.
3G
• 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.
is driven for C , a counter executes down-counting. When M8
M8200
RST C200
C200 K-5
Y001 Set value (constant)
It can be specified
indirectly also.
PLCs, latched type counters are backed up by the battery built into the PLC.
→ For details on backup methods against power failure, refer to Section 2.6.
X012
Up counting
Down counting
X013
X014
4 5 4
Current 3 3
2 2
value
1 1
0
0
When output has
been already
activated.
Y001
4 Devices in Detail
4.6 Counter [C]
is not driven, a
Up counting
−1
−2
−3 −4 −4 −3
−5
−6 −5
−6
−7 −7
−8
1
2
3
4
0
5
6
7
8
9
10
105