Function Parameters - Absolute Encoders (Ssi) - Siemens SIMATIC S7-300 Manual

Description of Functions
9.6.2 Absolute encoders (SSI)
Overview
Absolute encoders (SSI) have several significant advantages over incremental
encoders:
Absolute encoders
You can use 13-bit single-turn encoders, or 25-bit multi-turn encoders with
(SSI) the SSI protocol.
Function parame- Table 9-11 shows you how to adapt the selected encoder to the
ters FM 354.
Table 9-11
10
11
12
13
14
9-64
Longer cable lengths
Reliable data capture by using a single-step GRAY code
No encoder synchronization needed.
Absolute encoder (SSI) on linear axes
Make sure the value range of the encoder is at least equal to the traversing
distance of the axis.
Absolute encoder on rotary axes
Make sure that the absolute value range captured by the encoder corre-
x
sponds to a ratio of 2 or 2
it encompasses at least one rotary axis revolution (see "Dependencies"
Section 5.3.1 and Figure 9-5).
Function parameters – Absolute encoders (SSI)
MD Designation
Encoder type 3 = Absolute encoder (SSI 13 Bit)
4 = Absolute encoder (SSI 25 Bit)
13 = Absolute encoder (SSI 13 Bit)
14 = Absolute encoder (SSI 25 Bit)
Displacement per 1...1 000 000 000
encoder revolu- see Section 5.3.1, Dependencies
tion (division pe-
riod)
Residual distance 0...2
per encoder revo- see Section 5.3.1, Dependencies
lution
1
Increments per 2 ...2
encoder revolu- see Section 5.3.1, Dependencies
tion (division pe-
riod)
Number of revo- 0/1 =
1
lutions of 2 ...2
SSI encoder
–x
to one revolution of the rotary axis, and that
Value/Meaning
32
–1
25
Single-turn encoder
12
for multi-turn encoder
FM 354 Servo Drive Positioning Module
Comments/Unit
GRAY Code
GRAY Code
Binary Code
Binary Code
(MSR)
(integer portion)
–32
(2 MSR)
(fractional portion)
Entry according to
encoder rating plate
Only powers of 2
allowed