Siemens SIMATIC FM 351 - Page 76

Machine Data and Incremental Dimensions
8-16
FM 351 Positioning Module
C79000-G7076-C351-02
Address Name Type Initial Value Comment
32.0 INC_REV DINT L#500 Increments per encoder revolution:
Range of values:
1 to 2
25
The “increments per encoder revolution” machine data specifies the number of increments output by an
encoder per revolution. Based on this value and the machine data “distance per encoder revolution”, the
FM 351 can calculate the resolution.
Incremental encoders
Any value from the range shown can be entered. One increment involves 4x decoding by the module
(see also Section 10.1, page 10-2).
Absolute encoders
For the limits there is a difference between the various encoder models: Only values in steps of a power
of two are allowed as input.
• Single-turn encoders with (number of revolutions = 1) 13-bit frame length:
– Minimum value = 4
– Maximum value = 8192
• Multiturn encoders (number of revolutions > 1) with 25-bit frame length:
– Minimum value = 4
– Maximum value = 8192
• Single-turn encoders with 25 bit frame length, no. of revs. = 1
– Minimum value = 4
– Maximum value = 2
25
Linear scales are assigned parameters as follows as multiturn encoders:
• Increments per encoder revolution = 8192
• Number of revolutions × 8192 ≥ number of steps of the linear scale
Address Name Type Initial Value Comment
36.0 NO_REV DINT L#1 Number of encoder revolutions:
Range of values:
1 (single-turn encoder)
2 to 4096 in powers of 2 (multiturn encoder)
The machine data “number of encoder revolutions” is only used for absolute encoders. You use it to
define the number of revolutions possible with this encoder.
The total number of steps of the encoder does not belong to the machine data.
It is calculated as follows:
Total number of steps = increments per encoder revolution × number of revolutions