Frequency Measurement - IDEC MICROSmart FC6A Series User Manual

5: F S
UNCTIONS AND ETTINGS

Frequency Measurement

This section describes frequency measurement, which measures the frequency of pulses input to an external input. Frequency
measurement is a function that measures the frequency of pulses input to an external input.
These input pulses are processed with dedicated hardware device in FC6A Series MICROSmart, so frequencies can be measured
with no relation to the scan time. The measurement results are stored in special data registers and they are updated with each
scan.
Function Specification
The FC6A Series MICROSmart external inputs are used by switching between normal input, high-speed counters, catch input,
interrupt input, and frequency measurement. To use frequency measurement, specify the relevant group as Frequency
Measurement in the WindLDR Function Area Settings.
Frequency measurement can be used with the following external inputs.
The frequency measurement results are stored in the following special data registers for each external input group.
All-in-One CPU module
Group
External Input
Frequency Measurement
Value
Frequency Measurement
Range
Measurement Error
Calculation Cycle
Upper
Frequency
Word
Measurement
Value
Lower
(32 bits)
Word
*1 Can be used as a normal input.
Plus CPU module
Group
External Input
Frequency Measurement
Value
Frequency Measurement
Range
Measurement Error
Calculation Cycle
Upper
Frequency
Word
Measurement
Value
Lower
(32 bits)
Word
*1 Can be used as a normal input.
*2 Can be used only with the Plus 32-I/O type.
Notes:
R/W is the abbreviation for read/write. When R/W, it can be read and written. When R, it can only be read. When W, it can only be written.

To reflect the measurement results in the special data registers, a maximum of calculation cycle + scan time is required. However, when the

FRQRF instruction is used during ladder processing, the frequency value of the special data registers can be updated to the latest value. The
latest calculation result can be read within 250 ms regardless of the input frequency.
The data registers for the upper word and the lower word of the measurement value change according to the 32-bit data storage method

specified. For details, see "32-bit Data Storage Setting" on page 5-56.
5-40
1
I2 I0
*1
— Yes
4 Hz to 100 kHz
Less than ±10% (4 Hz or higher and less than 4 kHz), less than ±0.1% (4 kHz or higher)
Within 1 s (less than 4 kHz), within 250 ms (4 kHz or higher)
— D8210 D8192
— D8211 D8193
1 2
I2 I0 I1
*1
— Yes Yes
Less than ±10% (4 Hz or higher and less than 4 kHz), less than ±0.1% (4 kHz or higher)
Within 1 s (less than 4 kHz), within 250 ms (4 kHz or higher)
— D8210 D8192
— D8211 D8193
FC6A S MICROS
ERIES
2 3
I1 I3 I4
Yes Yes Yes
4 Hz to 5 kHz
D8218 D8222
D8219 D8223
3
*2
I13 I3
*1
— Yes
4 Hz to 100 kHz
— D8218
— D8219
U ' M FC9Y-B1722
MART SER S ANUAL
4 5
I5 I6
*1
— Yes
4 Hz to 100 kHz
— D8226
— D8227
4 5
I4 I5
*1
Yes —
D8222 — D8226
D8223 — D8227
6
I7
Yes
D8198
D8199
6
I6 I7
Yes Yes
D8198
D8199