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Position Decoding
Defining the hysteresis
The hysteresis can be preset in BCD in the data block in data byte DR 22 ( Section 7.3.3) in the
range 0 to 99. It applies to all tracks of a channel and is only transferred to the IP 240 during a
configuring pass.
Hysteresis
lower
track limit
Hysteresis range
In order to prevent the hysteresis from encompassing, the entire track value defined for the
hysteresis should be smaller than the minimum track width.
Influence of the hysteresis on interrupt generation
Interrupts are always generated when an assigned track is reached. Following generation of an
interrupt, the actual value must have exited the hysteresis range for the relevant track limit
before entry into a new track can generate an interrupt.
If the hysteresis for the original track is still in force when a new track is entered, no interrupt is
generated upon entry into the new track.
Influence of the hyteresis on the outputs
A hysteresis affects the outputs only when
•
the channel was configured with DIGn/8=1
(the IP 240 is to reset the outputs when the track is exited) and
•
the outputs were enabled for setting and resetting by the IP
(Control bit DAnF=0 and control bit DAnS=1 were transferred to the IP).
If a track is traversed without a reversal of the direction of travel, the associated output is set at
the first track limit and reset at the second track limit ( Fig. 7-6). This is also the case when the
second track limit lies within the hysteresis range of the first track limit.
Actual
value
Output
Dn
7-10
Hysteresis
Fig. 7-5. Track with Hysteresis
Entry into the track
Hysteresis
Hysteresis in force
Fig. 7-6. Switching an Output on Traversing a Track
Hysteresis
Hysteresis range
Exit from the track
Track width
Hysteresis
upper
track limit
EWA 4NEB 811 6120-02a
IP 240
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