Specifications

IP 240 Position Decoding
Aborting a reference point approach
The reference point approach initiated by setting the REFF bit is normaly terminated, following
synchronization, with a negative-going edge at the preliminary contact input.
If, despite this, it is still necessary to exit a reference point approach, this can be done by resetting
the REFF bit:
• If the REFF bit is set to ”0” and forwarded to the IP before the positive-going edge is present
at the preliminary contact input, the reference point approach is aborted immediately and
actual value acquisition with track comparison initiated.
• If the REFF bit is set to ”0” and forwarded to the IP after the positive-going edge was already
present at the preliminary contact input, the reference point approach is not aborted until the
preliminary contact input shows a negative-going edge. If a valid condition for synchroniza-
tion occurs in the interim, the actual value is synchronized and the SYNC bit set.
Fig. 7-10. Sequence Diagram for Reference Point Approach
t
2
t
1
IN signal
Z signal
Status bit
SYNC
Counting
pulse
Actual value
when NVER=0
when NVER=0
0 1 2 to 99 0 1 2 3 to 100 101
20 21 22 to 119 20 21 22 23 to 120 121
Actual value
acquisition with
track comparison
Acquisition of the preliminary
contact signal
Actual value
acquisition with
track comparison
Control bit
REFF
Reference point
approach without
track comparison
Note
By selecting the traverse speed during the reference point approach and justifying
the negative-going initiating contact edge between two zero marks, you must
make sure that synchronization always takes place at the same zero mark position.
During reference point approach, the Z signal is evaluated when A=1 and B=1.
For information and conventions relating to the location and to the timing of the Z
signal and to acquisition of the preliminary contact signal, see Chapter 13 ”Encoder
Signals”.
Synchronization is possible in both traversing directions.
EWA 4NEB 811 6120-02a 7-17