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Chapter 13 Control Sub Functions
13.7.7 Pre-reading start function
The "pre-reading start function" does not start servo while the execution prohibition flag
is ON if a positioning start request is given with the execution prohibition flag ON, and
starts servo within operation cycle after OFF of the execution prohibition flag is
detected. The positioning start request is given when the axis is in a standby status,
and the execution prohibition flag is turned OFF at the axis operating timing.
The "pre-reading start function" will be explained below.
[1] Controls
[2] Precautions during control
[3] Program examples
[1] Controls
The pre-reading start function is performed by turning ON the positioning start
signal with the execution prohibition flag ON, or by executing the dedicated
instruction (ZP.PSTRT1, ZP.PSTRT2, ZP.PSTRT3, and ZP.PSTRT4). However,
if positioning is started with the execution prohibition flag ON, the positioning data
is analyzed but servo start is not provided. While the execution prohibition flag is
ON, "[Md.26] Axis operation status" remains unchanged from "5: Analyzing". The
servo starts within operation cycle after the execution prohibition flag has turned
OFF, and "[Md.26] Axis operation status" changes to the status (e.g. position
control, speed control) that matches the control system. (Refer to Fig.13.48)
Signal QD77MS2/QD77MS4 QD77MS16
Execution prohibition flag Y14, Y15, Y16, Y17
[Cd.183] Execution prohibition flag
[QD77MS4 operation example]
V
Positioning start signal
[Y10,Y11,Y12,Y13]
Execution prohibition flag
[Y14,Y15,Y16,Y17]
BUSY signal
[XC,XD,XE,XF]
OFF
OFF
ON
t
Ta
OFF
ON
ON
Md. 26 Axis operation
status
Positioning start timing
Positioning data
analysis
Execution prohibition flag OFF waiting
Standby
Analyzing
Position control Position control
Operation cycle or less
(Note): Refer to Section 3.3 for input/output signal of QD77MS16.
Fig. 13.48 Operations of pre-reading start function