216
FX
3U
Series Programmable Controllers
User’s Manual - Hardware Edition
11 Use of High-speed Counters (C235 to C255)
11.7 Timing of Updating of Current Value and Comparison of Current Value
11.7
Timing of Updating of Current Value and Comparison of Current Value
11.7.1 Timing of updating of current value
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.
11.7.2 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 for counting operation, the value can be compared with time
*1
in
the main program by using 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 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 when the relevant high-speed counting operation. These
instructions have limitations on the number of simultaneously driven instructions as shown in the following
table. The HSCT instruction can only be used once in any program.
When the output relay (Y) has been designated for comparison results, the ON/OFF status of the output is
affected directly until END instruction output is refreshed.
When the PLC is a relay output type, a mechanical delay in operation (approx. 10ms) is caused. Therefore,
use a transistor output type PLC.
*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,
refer to Section 11.9.
Classification
Timing of updating of current value
Hardware counter
OUT instruction of counter
HCMOV instruction
Software counter
When count is input
Applied instruction
Limitation in number of instructions driven at same time
HSCS
32 instructions including HSCT instruction
HSCR
HSZ
*1
HSCT
*1
Only 1 (This instruction can only be used once.)
Summary of Contents for FX2-16E series
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