
SM-Universal Encoder Plus User Guide
15
Issue Number: 6
www.controltechniques.com
* Max input frequency = LPR x max rpm / 60
3.4.6
Comms only, (absolute encoders) SSI and EndAt
SSI, EndAt
Encoders with either an EndAt (transfer standard from Heidenhain) or SSI
(Synchronous Serial) interface can transmit data synchronised with a CLOCK signal
provided from the drive. This makes it possible to transmit position values quickly and
reliably with only four signal lines.
The main difference between the SSI and the EndAt being that the standard SSI
encoder is Uni-directional whereas the EndAt is Bi-directional. The data transfer for both
the SSI and the EndAt takes the form of EIA Standard RS 485.
The SSI (Synchronous Serial interface) and EndAt (Encoder Data) encoders have a
serial link between the encoder and drive which passes all positional information.
The encoder operates in the following manner:
1.
A clock signal at a user defined frequency is sent out to the encoder.
2.
Once a downward latching signal is detected by the encoder.
3.
Followed by the data request.
4.
The encoder then returns data to the drive at the clock frequency.
Limitations
Type
Encoder
Max Input Frequency *
Max no. of
Lines (LPR)
Max Baud
Rate (bits/s)
Incremental plus
commutation
SC.HiPEr
115khz (full resolution)
250kHz (reduced resolution)
50,000
9600k
SC.EndAt
2M
SC.SSI
The maximum speed in rpm which an encoder connected to the SM-Encoder Plus can
reach can be calculated from:
Max rpm = (60 x Max input frequency) / Encoder LPR
e.g. For a 4096 line encoder the maximum rpm would be:
(60 x 600 x 10
3
) / 4096 = 8789rpm
NOTE
The absolute maximum input frequency for any SC, SinCos encoder used with the SM-
Universal Encoder Plus is 250 kHz.
NOTE
Type
Encoder
Description
Pr x.15
Comms
(absolute)
EndAt
Absolute EndAt only encoder
Additional communications with the encoder is not
possible.
8
SSI
Absolute SSI only encoder.
Additional communications with the encoder is not
possible.
10
It should be noted that EndAt and SSI encoders must be initialised before their position
data can be used. The encoder is automatically initialised at power-up, after trips 1 - 8
are reset, or when the initialisation parameter (Pr
3.47
) is set to 1. If the encoder is not
initialised or the initialisation is invalid the Solutions Module initiates a trip 7, and the drive
will trip on SLX.Err.
NOTE
Содержание SM-Universal Encoder Plus
Страница 73: ...SM Universal Encoder Plus User Guide 73 Issue Number 6 www controltechniques com ...
Страница 112: ...0471 0005 06 ...