Function Description; Matching Module For Incremental Encoders - Siemens SIMATIC S5 Equipment Manual

3.1

Function Description

The signals arriving from the encoders via channel A and B are converted to ITL level in the input–
conditioning circuit.
Depending on the selected operating mode, the signals are initialized in the directional logic.
Encoders with the following signals can be used:
– Two pulse trains with 90° displacement
– Neutral pulses (1 pulse train, 1 direction signal)
– Direction–sensitive pulses (1 pulse per direction)
The required settings are shown in section 3.3.1.
Incremental encoders provide pulses only; therefore after initial turn–on or power failure, the 1P
241 has no system reference (i.e., no reference point is available). The reference point can be es-
tablished in two ways:
– By hardware–based synchronization (see section 3.3.5).
– By software-based synchronization (see section 3.3.6).
The drive direction for hardware–based synchronization can be selected on the matching module
for the encoder; see section 3.3.1 (switch S2) "sign synchronization". This presetting is required,
for example, to eliminate spindle play of your system when the reference point is approached.
In each data block a zero shift (NV value) can be specified separately for each channel. This value
is then stored in the synchronization memory of the matching module for the encoder.
The synchronization enable is activated with the SH command in standard FB 157. The pP of the
basic module transfers this enable via "TVS" to directional logic and synchronization logic.
The synchronization logic compares the sync sign, the encoder zero mark and the initiating sys-
tem pulse with the drive direction detected by the directional logic.
When they coincide, the value of the synchronization memory is accepted by the up/down
counter.
When the synchronization is completed (see Time Requirements for Synchronization in section
8.3), additional encoder pulses effect a change of the up/down counter contents.
The value of this fast up/down counter is continuously transferred to a 3– byte scan memory.
The transfer is interrupted only as long as the VP reads the 3 bytes.
Counter operation and sampling are separated by a clock pulse.
The actual value transferred to the basic module is compared with the track setpoints (cams)
there.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

Matching Module for Incremental Encoders

3 – 1