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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.8 High Speed Counter [C] (FX3G PLCs)
4.8.3 Handling of high speed counters
High speed counters in FX3G PLCs operate in the same way as high speed counters in FX3U/FX3UC PLCs.
For details, refer to the following.
→ 4.7.3 Handling of high speed counters
4.8.4 Current value update timing and comparison of current value
1. Current value update timing
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.
2. Comparison of the Current value
The following two methods are available to compare and output the current value of a high speed counter.
1) Using the comparison instruction (CMP), zone comparison instruction (ZCP) or comparison contact instruction
Use the comparison instruction (CMP), band comparison instruction (ZCP) 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.
If it is necessary to execute comparison to update an output contact with the high-speed counter's changing value,
use comparison instructions for high speed counters HSCS, HSCR and HSZ.
2) Using comparison instructions for high speed counters (HSCS, HSCR or HSZ)
The comparison instructions for high speed counters (HSCS, HSCR and HSZ) execute a comparison and output
the comparison result during high speed counting. The number of times these instructions can be used is limited
as shown in the table below.
When an output relay is specified for the comparison result, the comparison result is directly updated at the ON/
OFF status of the output regardless of the output refresh by END instruction.
Mechanical operation delay (about 10 ms) cannot be avoided in a relay output type PLC. Use a transistor output
type PLC.
4.8.5 Related devices
1. Devices used to switch the counting direction of 1-phase 1-count input counters
Instruction Limitation in number of instruction
HSCS
Can be used up to 6 times.HSCR
HSZ
Type Counter No. Specifying device Up-counting Down-counting
1-phase
1-counting input
C235 M8235
OFF ON
C236 M8236
C237 M8237
C238 M8238
C239 M8239
C240 M8240
C241 M8241
C242 M8242
C243 M8243
C244 M8244
C245 M8245