Changing The Logic Of External Reset Input Signal; Assignment Of Counter Input Terminal And Switching Of Function - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
4.7.6

Changing the logic of external reset input signal

The counters C241 to C245, C247 to C250 and C252 to C255 are usually reset when the external reset input
turns ON.
By using the program shown below, the logic can be inverted so that these counters are reset when the
external reset input turns OFF.
Counter No.
C241 to C245
C247 to C250
C252 to C255
Caution
The counter C253 is switched to a software counter when the logic of the external reset input signal is
inverted.
4.7.7

Assignment of counter input terminal and switching of function

The assignment of the input terminal and the function of the software counters C244, C245, C248 and C253
are changed as shown below when combined with the following special auxiliary relays.
In a program, put a special auxiliary relay just before a target counter.
Counter No.
C244(OP)
C245(OP)
C248(OP)
C253(OP)
116
When inverting logic of external reset input signal
M8388
When using software counter as hardware counter
M8388
M8390
C244
K
M8388
M8391
C245
K
M8388
M8392
C248
K
M8388
M8392
C253
K
4.7 High Speed Counter [C] (FX3U/FX3UC PLC)
M8389
C2
K
4 Devices in Detail
Description
The logic of the external reset input is
inverted so that the counters are reset
when the input turns OFF.
(The logic is inverted for all target
counters.)
Description
• The counting input is changed from
X000 to X006.
• Reset input is not provided.
• Start input is not provided.
• It operates as a hardware counter.
• The counting input is changed from
X002 to X007.
• Reset input is not provided.
• Start input is not provided.
• It operates as a hardware counter.
• Reset input is not provided.
• It operates as a hardware counter.
• Reset input is not provided.
• It operates as a software counter.