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Positioning
Zero mark monitoring
Zero mark monitoring is used to detect spurious or missing pulses, and is possible only when
•
the number of encoder pulses between two zero marks (Z signals) is divisible by 4 or 5 without
a remainder,
•
the timing of the zero mark signal satisfies the conditions discussed in Section 13.1 "Signal
Forms and Timing Requirements for Incremental Encoders" and
•
a reference point approach was terminated with synchronization.
If the IP 240 discovers that the number of pulses between two Z signals is not divisible by 4 or 5
without a remainder, it sets status bit NPUE (zero point monitoring).
Status bit NPUE remains set on the IP until it has been read out over the status area or interrupt
request bytes ( Section 10.17).
Initializing zero point monitoring
When you configure the channel, you must indicate whether or not you want zero mark monito-
ring, and which encoder you are using, by initializing FB 167's IMP parameter accordingly.
: JU FB 167
NAME : STRU.POS
:
:
IMP
: KF x
Zero mark monitoring must be deactivated when
•
the encoder cannot satisfy the timing requirements for the reference signal
•
the number of pulses between two Z signals is divisible by neither 4 nor 5.
Note
The IP checks for a wirebreak/zero mark error in every module firmware cycle. In
the event of an error,
•
the outputs are disabled and the positioning procedure currently in progress is
interrupted,
•
the position number is deactivated,
•
status bits BEE1, BEE2, BEE3 and RICH are set to "1",
•
status bit SYNC is set to "0".
The actual value must then be resynchronized.
10-34
x=0
No zero mark monitoring
x=10
The number of encoder pulses between two
zero marks is divisible by 5 without a remainder.
x=16
The number of encoder pulses between two
zero marks is divisible by 4 without a remainder.
IP 240
EWA 4NEB 811 6120-02a
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