Cautions On Use - Mitsubishi Electric MELSEC-Q Structured Programming Manual

FXCPU Structured Programming Manual
[Device & Common]

2.7.11 Cautions on use

• For a contact to drive the coil of a high speed counter, use a contact which is normally ON during high
speed counting.
Example : M8000(RUN monitor)
K
Program a contact which is
normally ON during counting.
• If the operation of a high speed counter is triggered by a device equipped with a contact such as simulation
switch, the counter may malfunction due to noise generated by chattering of the switch.
• The input filter of input terminals in the PLC main unit used for high speed counters are automatically set
as follows:
FX /FX
3U 3UC
FX /FX
3G 3GC
FX PLC: 10 µs (X000 and X001) or 50 µs (X002 to X007)
3S
FX /FX /FX
1S 1N
FX /FX /FX
0S 0
Accordingly, it is not necessary to use the REFF instruction or special data register D8020 (input filter
adjustment).
The input filter of input relays not used for high speed counters remain 10 ms (initial value).
• Inputs X000 to X007 (X003) are used for high speed counters, input interrupt, pulse catch, SPD/DSZR/
DVIT/ZRN instructions and general-purpose inputs.
Make sure to use each input terminal only once.
For example, when C251 is used, X000 and X001 are occupied. As a result, "C235, C236, C241, C244,
C246, C247, C249, C252 and C254", "input interrupt pointers I00* and I10*", "pulse catch contacts M8170
and M8171" and "SPD instruction using X000 and/or X001" cannot be used.
• When a counting input pulse is not provided, none of high speed counter output contacts does not turn ON
even if the PLC executes an instruction in the status "Current value = Set value".
• Counting can be started or stopped in a high speed counter when the output coil (OUT C**) is set to ON or
OFF. Program this output coil in the main routine.
If the output coil is programmed in a step ladder circuit, subroutine or interrupt routine, counting cannot be
started or stopped until the step ladder or routine is executed.
• Make sure that the signal input to a high speed counter does not exceed the response frequency described
above.
If an input signal exceeds the response frequency, a WDT error or parallel link (communication)
malfunction may occur.
• The response frequency changes depending on number of used counters, but the input filter value is fixed.
Note that noise above the response frequency may be counted depending on the filter value of the used input.
• When a high speed counter is reset by the RST instruction, it cannot execute counting until driving of the
RST instruction is set to OFF.
1) Program example
X010
2) Timing chart
X000
Current value
of C235
X010
RST
C235
92
OUT_C_32
EN ENO
CCoil
CC235
CValue
PLCs: 5 µs (X000 to X005) or 50 µs (X006 and X007)
PLCs: 10 µs (X000, X001, X003 and X004) or 50 µs (X002 and X005 to X007)
/FX /FX PLCs: 20 µs (X000 and X001) or 50 µs (X002 to X005)
1NC 2N 2NC
/FX /FX PLCs: 50 µs (X000 to X003 or X005)
0N U 2C
RST
EN ENO
d
The current value does not change even
3
if pulses are input because the C235
2
reset instruction is valid.
1
Driving of "RST C235" is set to ON
because the contact turns ON.
Input number corresponding to C235
X000
CC235
K
CC235
C235 remains reset.
2 Devices in Detail
2.7 High Speed Counter [C]
OUT_C_32
EN ENO
CCoil
CValue
3
2
1
Driving of "RST C235" is set to OFF
because the contact turns OFF.