Omron FQM1-MMP21, FQM1-CM001, FQM1-MMA21 Pulse Inputs, Section, Latching a High-speedCounter’s PV

Pulse Inputs Section 7-5

Latching a High-speed Counter’s PV

Frequency Measurement (Mode 2) Specifications

Item	Specifications
Applicable pulse	Only pulse 1 (high-speed counter 1) can be used.
input
Measurable frequen-	0 to 500 kHz
cies	Note When no pulses have been input for 10 s, the measured
	value is set to 0 Hz (stopped). The previous output
	value is retained during this 10-second interval.
Measurement period	5 ms max. (input frequency 500 Hz min.)
	Note At input frequencies below 500 Hz, the measurement
	period is increased to accommodate the lower input fre-
	quencies and becomes 200 ms max. for input frequen-
	cies of 10 Hz min.
Operating conditions	In the System Setup, set the pulse input’s counter data display
	to frequency measurement (mode 2).

The present counter value can be latched at the rising edge of the latch signal input and stored as the latch register value. Each time the counter value is captured, the latch register value is overwritten with the new value and the old value is lost.

To use the latched counter value (latch register value) in the ladder program, read the latch register value with the PRV(881) instruction.

Word	Bit	Function		Details
A608	08	High-speed Counter 1	Count Latched Flag
		Status Flag	Indicates that a high-speed counter
			PV has been captured in the latch
			register by the latch signal input.
A609	08	High-speed Counter 2	Count Latched Flag
		Status Flag	(This flag has the same function as
			the flag for high-speed counter 1.)
A610	08	High-speed Counter 1	Latch Input 1 Enable
		Command	OFF: Disabled
			ON:	Enabled
	09		Latch Input 2 Enable
			OFF: Disabled
			ON:	Enabled
A611	08	High-speed Counter 2	Latch Input 1 Enable
		Command	OFF: Disabled
			ON:	Enabled
	09		Latch Input 2 Enable
			OFF: Disabled
			ON:	Enabled

There is one latch register provided for each counter.

Both latch input 1 and latch input 2 can be enabled for a single counter, but only latch input 1 will be effective when both inputs are enabled.

Two latch inputs can be used for a single counter by enabling/disabling latch input 1 and 2 from the ladder program to enable only the desired input when it is required. In this case, allow at least one Motion Control Module cycle between the use of the two inputs.

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