Timing Of Updating Of Current Value And Comparison Of Current Value; Timing Of Updating Of Current Value; Comparison Of Current Value - Mitsubishi Electric MELSEQ FX3S Series User Manual

FX Series Programmable Controllers
3S
User's Manual - Hardware Edition
10.6

Timing of Updating of Current Value and Comparison of Current Value

10.6.1 Timing of updating of current value

When pulses are input to an input terminal for a high-speed counter, the high-speed counter executes up-
counting or down-counting. The current values of devices are updated when counting is input.

10.6.2 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 instruction), band comparison instruction
(ZCP instruction) or contact comparison instruction
Use the comparison instruction (CMP instruction), band comparison instruction (ZCP instruction) or contact
comparison instruction if the comparison result is necessary at counting. Use these instructions only when
high-speed processing is not required because these instructions are processed in the operation cycle of the
PLC, and operation delay is generated before the comparison output result is obtained. Use the comparison
instructions for high-speed counters (HSCS instruction, HSCR instruction and HSZ instruction) described
below if it is necessary to execute comparison and change the output contact (Y) at the same time when the
current values of high-speed counters change.
2. Use of Comparison instruction for high-speed counters
(HSCS instruction/HSCR instruction/HSZ instruction)
Comparison instructions for high-speed counters (HSCS instruction, HSCR instruction and HSZ instruction)
perform comparison and output the comparison results with the relevant high-speed counting operation.
These instructions have limitations on the number of simultaneously driven instructions 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. 10 ms) is caused.
Therefore, it is best to use a transistor output type PLC.
Applied instruction
*1
HSCS instruction
*1
HSCR instruction
*1
HSZ instruction
*1. The overall frequency changes when the HSCS instruction, HSCR instruction or HSZ instruction is
used.
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10.6 Timing of Updating of Current Value and Comparison of Current Value
Limitation in number of instructions driven at same time
6 instructions
→ For details on the overall frequency, refer to Section 10.7.
10 Use of High-speed Counters