Mitsubishi FX3UC SERIES User Manual page 161

FX Series Programmable Controllers
3UC
User's Manual - Hardware Edition
*4. The 2-phase 2-count input counters are 1 edge count counters. The use of special auxiliary relays
changes them to 4 edge count counters.
→ For the procedures on operating them as 4 edge count counters, refer to Subsection 5.5.7.
2. Restriction of redundant use of input numbers
The input terminals X000 to X007 can be used for high-speed counters, input interruption, pulse catch, SPD,
ZRN, DSZR and DVIT instructions and general-purpose inputs. Take care not to overlap the input numbers.
For example, when C251 is used, X000 and X001 are occupied. Therefore, it is impossible to use C235,
C236, C241, C244, C246, C247, C249, C252 and C254, input interruption pointers I000 and I101, pulse catch
contacts M8170 and M8171 and SPD, ZRN, DSZR and DVIT instructions at the same time.
5.5.3 Current Value Update Timing and Comparison of Current Value
1. Current value update timing
When a pulse is input to a high-speed counter input terminal, the counter increments or decrements. The
current value of the device is updated at the timing shown in the following table.
Therefore, when the hardware counter directly handles the current value of the high-speed counter for MOV
instruction or CMP instruction or an applied instruction (such as a contact comparison instruction), it uses the
current value updated at the timing shown in the following table. As a result, the counter operation is affected
by the scan time.
Classification
Hardware counter
Software counter
2. Comparison of current value
To compare and output the current value of a high-speed counter, the following two methods are available.
1) Use of comparison instruction (CMP), band comparison instruction (ZCP) or contact comparison
instruction
When the comparison results are necessary during counting operation, the value can be compared with
*1
the time in the main program by using the HCMOV instruction just before a comparison command (CMP
command/ZCP command) or a contact comparison instruction.
*1. To compare the value with the high-speed counter's changing value and to change the output contact
(Y), use a Comparison instruction for high-speed counters (HSCS/HSCR/HSZ/HSCT instruction).
2) Use of Comparison instruction for high-speed counters (HSCS/HSCR/HSZ/HSCT instruction)
Comparison instructions for high-speed counters (HSCS, HSCR, HSZ and HSCT instructions) perform
comparison and output the comparison results with the relevant high-speed counting operation. These
instructions have limitations on the number of times of use as shown in the following table.
When the output relay (Y) has been designated for comparison results, the ON/OFF status of the output
is affected directly until the END instruction output is refreshed.
When the PLC is a relay output type, a mechanical delay in operation (approx. 10ms) is caused.
Therefore, it is best to use a transistor output type PLC.
Applied instruction
HSCS
HSCR
*1
HSZ
*1
HSCT
*1. When HSZ or HSCT instruction is used, the maximum response frequencies and overall frequency
of all software counters becomes limited.
→ For the maximum response frequencies and overall frequency of software counters,
Current value update timing
OUT instruction of counter
HCMOV instruction
Every time a pulse is input
Limitation on number of times of use of instruction
Up to 32 times including the number of times of use of
HSCT instruction
Only once
5 Input Specifications and External wiring
5.5 High-speed Counters (C235 to C255)
refer to Subsection 5.5.9.
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