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Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
24 Others – FNC181 to FNC189
24.5 FNC189 – HCMOV / High Speed Counter Move
2. High speed counter current value update timing and the effect of DHCMOV instruction
1) High speed counter current value update timing
When a pulse is input to an input terminal for a high speed counter (C235 to C255), the high speed
counter executes up-counting or down-counting.
If the current value of a high speed counter is handled in an applied instruction such as the normal MOV
instruction, the current value is updated at the timing shown in the table below. As a result, it is affected
by the program scan time.
By using DHCMOV instruction, the current value can be updated and transferred when it is executed.
2) Effect of DHCMOV instruction
• By using both input interrupt and DHCMOV instruction, the current value of a high speed counter can
be received at the rising edge or falling edge of an external input (at reception of input interrupt).
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Refer to the Program example 2.
• When DHCMOV instruction is used just before a comparison instruction (CMP, ZCP or comparison
contact instruction), the latest value of a high speed counter is used in comparison.The following points
must be kept in mind when using the DHCMOV command.
- When the current value of a high speed counter is compared using CMP, ZCP or comparison
contact instruction (not using a designated high speed counter comparison instruction), a hardware
counter does not change into a software counter.
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For the condition in which a hardware counter is handled as a software counter,
refer to Subsection 4.7.9.
- When the number of high speed software counter comparison instructions is reduced, the total
frequency limitation is decreased.
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For the limitation in software counters by the total frequency,
refer to Subsection 4.7.10.
- When it is necessary to execute comparison and change an output contact (Y) as soon as the
current value of a high speed counter changes, use a desighnated high speed counter comparison
instruction (HSCS, HSCR or HSZ).
- DHCMOV instruction can be used as many times as necessary.
Current value update timing
Hardware counter
When OUT instruction for the counter is executed
Software counter
Every time a pulse is input