Mitsubishi Electric MELSEC FX3U Programming Manual page 375

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2) FX PLCs
3G
When the HSCR instruction is used in FX
Refer to the counting operation described below, and select according to the contents of control whether
to use the HSCR instruction or a general-purpose comparison instruction.
a) Case to select the HSCR instruction
- When the output should be given if the counting result becomes equivalent to the comparison
value without regard to the scan time of the PLC
b) Cases to select a general-purpose comparison instruction
- When counting is regarded as important, but the effect of the scan time can be ignored in
operations according to the counting result
- When an instruction is used 6 times or more
FNC229
LDD<=
M8000
2. Only 32-bit operation instructions are available.
Because instructions for high speed counters are dedicated to 32 bits, make sure to input "DHSCR (FNC 54)".
3. Priority order in operation among HSCS (FNC 53), HSCR (FNC 54), and HSZ (FNC 55)
instructions for the same high speed counter
→ For details, refer to "6. Priority order in operations among HSCS (FNC 53), HSCR (FNC 54), and HSZ
4. Reset operation by an external terminal
→ For details, refer to "5. Reset operation by an external terminal [M8025*1: HSC (external reset)
5. Other cautions on using HSCR instruction
Program example
1. Example of self-reset circuit
When the current value of C255 becomes "400", C255 is immediately reset. Its current value becomes "0",
and the output contact is set to OFF.
M8000
C255
RUN monitor
FNC 54
DHSCR
3G
K10000 C251
FNC 50
REF
(FNC 55) instructions for the same high speed counter" in Subsection 13.4.1.
K300
K400 C255 C255
Comparison Comparison Output
value source destination
13 High Speed Processing – FNC 50 to FNC 59
13.5 FNC 54 – HSCR / High Speed Counter Reset
PLCs, the total frequency of each counter is affected.
RST Y010
Y010 K8
→ For details, refer Subsection 13.4.1.
Reset value of DHSCR
400
Count-up value
300
Current value
of C255
Output contact
of C255
mode]" in Subsection 13.4.1.
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