Mitsubishi Electric MELSEC iQ-F FX5 - Page 258

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25 HIGH-SPEED INPUT/OUTPUT FUNCTION
25.1 High-speed Counter Function
Parameters are enabled when the CPU module is powered ON or after a reset. In addition, operations
different from the parameter settings are possible by transferring values to special relays and special registers
while changing these values in the program.
For details concerning special relays and specials registers for high-speed counters, refer to Page 685
Special Relay List, Page 719 Special Register List.
Rotational speed measurement mode start/stop
The rotational speed measurement mode cannot measure by setting the parameter alone.
The HIOEN/DHIOEN instruction is required to start/stop measurement.
For the HIOEN/DHIOEN instruction, refer to MELSEC iQ-F FX5 Programming Manual (Instructions, Standard Functions/
Function Blocks).
Rotational speed
Rotational speed is stored in the special register for each channel. (Unit: r/min)
For details concerning specials registers for high-speed counters, refer to Page 719 Special Register List.
Precautions
■Count direction switch during measurement
The rotational speed measurement mode calculates rotational speed based on current value difference of high-speed
counters in the measuring unit time. You should therefore note that the input number of pulses may differ from the
measurement value when count direction of a high-speed counter is switched within the same measuring unit time.
■Operation when counting in the minus direction
Rotational speed can also be measured when pulses are input in the direction whereby current value of high-speed counter is
reduced.
■Operation at overflow of high-speed counter current value
Rotational speed measurement can continue even when current value of high-speed counter overflows during measurement.
■Relationship with the SPD/DSPD instruction
If rotational speed measurement has already been started by the HIOEN/DHIOEN instruction, the SPD/DSPD instruction
cannot be used for the same channel.
Inversely, if pulse density is currently being measured by the SPD/DSPD instruction, rotational speed measurement cannot be
started for the same channel.
For details on the SPD/DSPD instruction, refer to MELSEC iQ-F FX5 Programming Manual (Instructions, Standard
Functions/Function Blocks).
■Other precautions
There are common precautions when using high-speed counters. For details, refer to Page 288 Precautions when using
high-speed counters.
Enable Input Enable/
Disable
Set whether to "enable" or "disable" the enable input. • Disable
• Enable

Input logic Set the enable input logic value. • Positive Logic
• Negative Logic

Ring Length Enable/
Disable
Not available for high-speed counters (rotational speed
measurement mode).

Ring Length
Measurement Unit Time Set measurement unit time. (Unit: ms) 1 to 2147483647 
No. of Pulse per Rotation Set the No. of pulses per rotation. (Unit: pulse) 1 to 2147483647 
Item Description Setting range Default