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IP 240
Invoking the interrupt servicing OBs in the S5-150U and S5-155U PLCs (150 mode)
In the S5-150U and S5-155U (150 mode), the associated interrupt servicing OB is invoked at the
next block boundary when one of the bits in I/O byte 0 changes its values. Use the ABIT parameter
in configuring FB 169 to specify whether the OB is to be invoked every time the bit changes its
value or only when it goes from 0 to 1.
ABIT parameter
ABIT
: KY x,y
•
x>0
: Invoke OB on every signal change
•
x=0, y=0 to 7
: Invoke OB only on a signal change from 0 to 1.
7.2.8
Track Comparison Following Configuring and in the Event of an Error
Following configuring, the actual value is set to "0" and the encoder pulses are counted without
further synchronization. The computed actual value is compared to the specified track limits and,
depending on the actual value, reference bits are set, interrupts generated, and outputs set.
To prevent the generation of interrupts, you can mask all interrupts for the channel by trans-
ferring AMSK=1 or terminate the interrupt service routine after reading out the interrupt
request bytes.
You can enable setting of the outputs via the reference bits with control bits DAnF and DAnS.
Errors following transfer of a zero offset
Should a signal acquisition error (DRBR signal) or overrange error occur following configuring or
following transfer of a zero offset, the comparison of the updated actual value with the track
limits is aborted and the current status of the reference bits frozen.
A subsequent transfer of a zero offset reinitiates the track comparison, and the reference bits are
updated. The outputs are set in dependence on the actual value.
Following an overrange error, transfer of a zero offer is equivalent to returning the actual value
from overrange to normal range.
Error following a reference point approach
After configuring, the measuring system can be synchronized to a reference point via reference
point approach ( Section 7.2.9).
If a signal acquisition error or overrange error occurs following synchronization (DRBR or NPUE
signal), the comparison of the actual value to the reference tracks is aborted and the reference
bits are frozen. The comparison and setting of the outputs can be reenabled via a new reference
point approach or by transferring a zero offset.
Following a DRBR error, the next zero mark pulse may also produce an NPUE error, even when a
new reference point approach was initiated.
EWA 4NEB 811 6120-02a
In place of y you must enter the number of the bit in PY 0 which you set on
switchbank S1 ( Section 5.1.2).
Position Decoding
7-15
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