Siemens SIMATIC FM 351 Installation Manual page 101

Table 8-4 Machine Data for the Encoder, continued
Machine Data and
Assignment
No. of revolutions This machine data is only required for absolute encoders. You use it to define the num-
ber of revolutions possible with this encoder.
1, 2, 4, 8, 16, 32, 64,
128, 256, 512, 1024, If you would like to know more about absolute encoders, please read Chapter 10.3 of
2048, 4096
this manual.
Single-turn encoders
If you have set the 13 bit encoder, the value is permanently fixed at 1.
Multiturn encoders
If you have set a 25 bit absolute encoder, set the power-of-two value from 1 to 4096.
Please ensure that the total number of encoder steps is not exceeded.
Total no. of encoder steps The total number of steps is not an item of machine data. It is found from the two data
items:
Monitoring In operation the FM 351 monitors the connected encoder for:
Wire breakage (5 V sig-
nals)
Error pulse from incre- Error pulse from incre
Wire breakage
mental encoders (zero
With the activation of the monitoring the FM 351 monitors for an incremental encoder
mark monitoring)
the signals A, A, B, B, N and N. The monitoring detects:
Error pulse from incremental encoders
An incremental encoder must always supply the same number of increments between
two following zero marks.
The FM 351 checks whether the zero marks of an incremental encoder occur at the
correct point in time.
FM 351 Positioning Function Module
EWA 4NEB 720 6001-02
Increments per encoder revolution.
Number of revolutions.
Total no. of steps = Increments per encoder rev. No. of revs.
Wire breakage
Error pulse
Wire breakage
Short circuit on the separate lines.
Interval between the edges of the counting pulses.
Failure of the encoder supply.
Machine Data and Increments
Description
8
8-15