Rockwell Automation 1771-QB Linear Pos. - Manual (Page 88)

Formatting Module Data (WRITES)
Chapter 7
7Ć9
Important: If you change the axis polarity, exchange the forward and reverse
analog calibration constants. The zero-position offset defines the direction of
forward and reverse motion.
Calculate the zero-position offset by measuring the distance between the
zero-position and the transducer’s head, as shown above. The module accepts a
maximum of +799.900 inches (+7999.00 millimeters). The sign defines whether
the transducer head is on the positive or negative end of the axis. If the
zero-position offset is zero, then the positive direction is away from the
transducer head, in the extend direction.
Figure 7.7
ZeroĆPosition Offset Words
50029
ZeroĆposition offset,
BCD or binary
799.900 inches or 7999.00 mm max
Most significant digits Sign:
0 = +
1 = -
Sign:
0 = +
1 = -
Least significant 3 digits
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Important: If you select binary format, both words are represented as
2’s-complement integers compatible with the PLC-5. See Appendix H for
examples of these words.
Software Travel Limits (words 9, 10 and 38, 39)
When a setpoint command calls for the axis to move beyond a software travel
limit, the module aborts the move and reports a programming fault. When a jog
command calls for the axis to move beyond a software travel limit, axis
movement will decelerate and stop at the limit.
The software travel limits must be within the active range of the transducer. The
active range of your transducer is halved by each increase in the number of
circulations of your digital interface box.