Cautions On Use - Mitsubishi FX3U Series Programming Manual

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

4.7.11 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 NO contact)
Program a contact which is
normally ON during counting.
• If the operation of a high speed counter is triggered by devices with contact such as simulation switch, the
counter malfunctions accurs due to chattering in the devices.
• The input filter of an input terminal for a high speed counter in the main unit is automatically set to 5 µs
(X000 to X005) or 50 µs (X006 and X007).
Accordingly, it is not necessary to use REFF instruction or special data register D8020 (input filter
adjustment).
The input filter of input relays not used for high speed counters keeps 10 ms (initial value).
• The inputs X000 to X007 are used for high speed counters, input interrupt, pulse catch, SPD/DSZR/DVIT/
ZRN instructions and general-purpose inputs. There should be no overlap between each input number.
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.
• As long as a counting pulse is not given, the output contacts don't turn ON at all high speed counters even
if the PLC executes an instruction in condition of "present value = set value".
• By setting to ON or OFF an output coil (OUT C***) in a high speed counter, counting can be started or
stopped. Program this output coil in the main routine. If this output coil is programmed in a step ladder
(SFC) circuit, subroutine or interrupt routine, counting cannot be started or stopped until such step ladder
or routine is executed.
• Make sure that signal speed for high speed counters does not exceed the response frequency described
above. If a signal beyond the response frequency is input, a WDT error may occur or parallel link
malfunction may accur.
• When a high speed counter is reset by RST instruction
The high speed counter cannot start counting unless the drive of RST instruction is set to OFF.
When only the current value should be cleared or when both the OFF status of a contact and the current
value should be reset, make the following programs:
- When only the current value should be cleared
X010
FNC 12
DMOV
- When both the OFF status of a contact and the current value should be reset
X010
C235
K0 C235
The current value of C235 is cleared (to "0").
C235 is reset.
RST C235
Contact: Set to OFF, Current value: Cleared to "0"
X010
Reset image of C235 is reset.
RST C235
Input number corresponding to
C235
X000
C235
If a number of input relay for counting is specified, high
speed counter cannot execute accurate counting.
4 Devices in Detail
4.7 High Speed Counter [C]
101
1
2
3
4
5
6
7
8
9
10