Frequency Ranges; Pulse Frequency Calculation Methods - Omron CJ1M-CPU21 Operation Manual

HIGH-SPEED COUNTER PV READ: PRV(881)
Variations
86
■ Reading Pulse Output or High-speed Counter Frequency (C = 00@3 hex)
If C is 00@3 hex, PRV(881) reads the frequency being output from pulse out-
put 0 or 1 or the pulse frequency (Hz) being input to high-speed counter 0 and
stores it in D and D+1.

Frequency Ranges

Value of C
0000 or 0001 hex
(Reading the frequency
of pulse output 0 or 1)
0010 hex
(Reading the frequency
of high-speed counter
input 0)

Pulse Frequency Calculation Methods

When the CPU Unit is a CJ1M CPU Unit with unit version 3.0 or later, there
are two ways to calculate the frequency of pulses output from pulse output 0
or 1 or pulses input to high-speed counter 0.
1. Standard Calculation Method (Earlier Method)
The count is calculated by counting each pulse regardless of the frequen-
cy. At high frequencies, the rising or falling edges of some pulses will be
corrupted, resulting in errors (roughly 1% error max. at 100 kHz).
2. High-frequency Calculation Method
In this case, the counting method is switched at high and low frequencies.
• High-frequency counting
At high frequencies (above 1 kHz), the function counts the number of
pulses within a fixed interval (the sampling time) and calculates the fre-
quency from that count. One of the following three sampling times can
be selected by setting the third digit of C.
Sampling time
10 ms
100 ms
1 s
• Low-frequency counting
At frequencies below 1 kHz, the Standard Calculation Method is used,
regardless of the sampling time setting.
Variations Executed Each Cycle for ON Condition
Executed Once for Upward Differentiation
Executed Once for Downward Differentiation Not supported
Immediate Refreshing Specification
Conversion result
0000 0000 to 0001 86A0 hex (0 to 100,000)
Counter input method: Any input method other than 4×
differential phase mode
Result = 00000000 to 000186A0 hex (0 to 100,000)
Note If a frequency higher than 100 kHz has been input,
the output will remain at the maximum value of
000186A0 hex.
Counter input method: 4× differential phase mode
Result = 00000000 to 00030D40 hex (0 to 200,000)
Note If a frequency higher than 200 kHz has been input,
the output will remain at the maximum value of
00030D40 hex.
Value of C
0013 hex Counts the number of pulses every 10 ms.
The error is 10% max. at 1 kHz.
0023 hex Counts the number of pulses every 100 ms.
The error is 1% max. at 1 kHz.
0033 hex Counts the number of pulses every 1 s. The
error is 0.1% max. at 1 kHz.
Section 5-2
Description
PRV(881)
@PRV(881)
Not supported