Omron SYSMAC CJ - REFERENCE MANUAL 08-2008 Reference Manual page 917

High-speed Counter/Pulse Output Instructions
Flags
Precautions
(If a frequency higher than 100 kHz has been input, the output will re-
main at the maximum value of 000186A0 hex.)
• Counter input method: 4 differential phase mode
Conversion result = 00000000 to 00030D40 hex (0 to 200,000)
(If a frequency higher than 200 kHz has been input, the output will re-
main at the maximum value of 00030D40 hex.)
2. Frequency Calculation Method
When the CPU Unit is a CJ1M CPU Unit with version number 3.0 or later,
there are two ways to calculate the frequency of pulses input to high-speed
counter 0.
a) Standard Calculation Method (C1 = 0@00)
The count is calculated by counting each pulse regardless of the fre-
quency. At high frequencies, the rising or falling edges of some pulses
will be corrupted, resulting in errors (about 1% error max. at 100 kHz).
b) High-frequency Calculation Method
In this case, the counting method is switched at high and low frequen-
cies. (Supported by CJM1 CPU Unit Ver. 3.0 or later only)
• High-frequency counting (C1 = 0@10, 0@20, or 0@30)
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 the third digit of C1.
Sampling time Value of C1
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.
Converting Counter PV to Total Number of Revolutions (C1 = 0001 hex)
If C1 is 0001 hex, PRV2(883) calculates the cumulative number of revolutions
from the counter PV and pulses/revolution setting.
Conversion result = Counter PV
Name Label
Error Flag ER
If the counter is reset when C1 specifies frequency-rotational speed conver-
sion for a high frequency, the data read during the sampling time when the
counter was reset will not be dependable.
0@10 hex Counts the number of pulses every 10 ms.
The error is 10% max. at 1 kHz.
0@20 hex Counts the number of pulses every 100 ms.
The error is 1% max. at 1 kHz.
0@30 hex Counts the number of pulses every 1 s. The
error is 0.1% max. at 1 kHz.
Pulses/revolution
Operation
ON if high-speed counter 0 is disabled in the settings.
ON if C1 is not in the specified range (0000 or 0001).
ON if the pulses/revolution setting in C2 is 0000.
Section 3-21
Description
877