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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
36 Interrupt Function and Pulse Catch Function
36.8 Pulse width/Pulse period measurement function [M8075 to M8079, D8074 to D8097]
*1. The ring counter offers 32-bit data including the most significant bit.
The DSUB (FNC21) instruction does not give a correct value because it handles the most significant
bit as the sign bit. To obtain a correct value, add the processing inside the dotted frame.
2. Cautions on use
• The pulse width/pulse period measurement function and input interrupts can be used at the same time in a
same input terminal.
• When a same input terminal is used by the pulse width/pulse period measurement function and the SPD
(FNC56), DSZR (FNC150) or ZRN (FNC156) instruction, an operation error occurs when the instruction is
executed.
• The input terminal used for the pulse width/pulse period measurement function cannot be used for the
pulse catch function.
• When a same input terminal is used by the pulse width/pulse period measurement function and a high
speed counter, a grammatical error occurs.
• Make sure that the total frequency of four input channels is 50 kHz or less when using the pulse width/
pulse period measurement function.
• When the pulse width/pulse period measurement function and a high speed counter are used together, the
overall frequency of the high speed counter is affected.
→ For details on high speed counters, refer to Subsection 4.8.7.
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