346
FX3G/FX3U/FX3GC/FX3UC Series
Programming Manual - Basic & Applied Instruction Edition
13 High-Speed Processing – FNC 50 to FNC 59
13.4 FNC 53 – HSCS / High-Speed Counter Set
13.4.1 Common cautions on using instructions for high-speed counter
DHSCS (FNC 53), DHSCR (FNC 54), DHSZ (FNC 55) and DHSCT (FNC280) instructions are provided for high-
speed counters.
This section explains common cautions for these instructions.
1. Limitation in the number of instances of each instruction in a program and number of
instructions driven at the same time
1) FX3U/FX3UC PLCs
DHSCS, DHSCR and DHSZ instructions can be used as many times as necessary in the same way as general
instructions. However, the number of simultaneously driven instructions is limited. The DHSCT instruction can
only be used once in any program.
2) FX3G/FX3GC PLCs
DHSCS, DHSCR and DHSZ instructions can be used as many times as necessary in the same way as general
instructions. However, the number of simultaneously driven instructions is limited.
2. Response frequency of high-speed counters
When the DHSZ or DHSCT instruction is used in FX3U/FX3UC PLCs, the maximum response frequency and total
frequency of every software counter are limited.
When the DHSCS, DHSCR or DHSZ instruction is used in FX3G/FX3GC PLCs, the total frequency of high-speed
counters is limited.
→ For the maximum response frequency and total frequency in FX3U/FX3UC PLCs, refer to Subsection 4.7.10.
→ For the total frequency in FX3G/FX3GC PLCs, refer to Subsection 4.8.7.
3. Specification of output numbers (Y)
When using the same instruction for high-speed counter repeatedly or when driving two or more other instructions for
high-speed counter at the same time, specify such output devices (Y) whose high-order two digits are the same (in
units of 8 devices).
1) When using devices of the same number (in units of 8 devices)
Example: When using Y000, specify Y000 to Y007. When using Y010, specify Y010 to Y017.
2) When using two or more instructions for high-speed counter and non-consecutive output (Y) numbers
A program example is shown below:
When C255 reaches K100, the output Y000 is driven by interrupt. Y010 is driven when END processing is
executed.
If interrupt drive is required, use an output number ranging from Y001 to Y007 whose high-order two digits are
equivalent.
Instruction Limitation in number of instructions driven at same time
DHSCS
32 instructions including DHSCT instructionDHSCR
DHSZ
DHSCT Only 1 (This instruction can only be used once.)
Instruction Limitation in number of instructions driven at same time
DHSCS
6 instructionsDHSCR
DHSZ
FNC 53
DHSCS
K100 C255 Y010
FNC 53
DHSCS
K100 C255 Y000
M8000
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