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PLC User's Manual - Positioning Control Edition
Built-in Positioning Functions
4 Before Programming
4.4 Current Value and Flag for Monitoring of Operation
B - 56
4.4 Current Value and Flag for Monitoring of Operation
4.4.1 Current Value
During positioning operation, use the current value register to check the current value positioning address.
The current value will be increased or decreased depending on the rotation direction. The following table
shows the current value register (32-bit) of each pulse output destination device.
*1. Y002 (pulse output destination) cannot be specified when the 14-point or 24-point type FX
3G PLC is
connected.
*2. Devices related to Y003 (pulse output destination) are only valid if two FX
3U-2HSY-ADP adapters are
connected to the FX
3U PLC.
Caution:
The current value changes between -2,147,483,648 and 2,147,483,647. However, if an overflow or
underflow occurs, the value changes as shown below. Check the value carefully.
• If the current value is increased past the maximum value, the minimum value will be indicated.
• If the current value is decreased below the minimum value, the maximum value will be indicated.
Necessity of zero return:
If the specified forward rotation pulse or reverse rotation pulse is output, the current value register will
increase or decrease the current value. Upon turning off the power of the PLC, however, the current value
stored in the current value register will be erased. For this reason, after turning the power on again, be sure
to adjust the current value of the current value register to the current position of the machine. For this
adjustment, use the zero return instruction or the Absolute Current Value Read instruction (absolute position
detection system) shown below:
→ For details on DSZR instruction, refer to Section 6.2.
→ For details on ZRN instruction, refer to Section 6.3.
→ For details on ABS instruction, refer to Chapter 7.
*3. The absolute position detection function applies for the MR-HA, MR-J2A MR-J2SA, or MR-
J3A servo amplifiers. If one of these servo amplifiers is used and mechanical zero return is
performed only once just before turning off the power, the current value will not be erased even after
power-off.
After turning on the power again, read out the stored current value using the ABS (FNC155)
instruction of the PLC. This means that the current value can be obtained without performing zero
return just after turning on the power again.
Pulse output destination device Current value register (32-bit)
Y000 D8341,D8340
Y001 D8351,D8350
Y002
*1
D8361,D8360
Y003
*2
D8371,D8370
Instruction Description
DSZR(FNC150) Zero return instruction with DOG search function
ZRN(FNC156) Zero return instruction (without DOG search function)
ABS(FNC155)
*3
Absolute Current Value Read instruction