Page 29 - Keubler Motion Sensors

Basics

Encoders Absolute encoders

Outputs To transfer the position data to a controller,
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different interfaces are available.
Product overview
Synchronous serial interface (SSI) Compared to the parallel interface, the SSI interface In addition less lines are needed for transmission Basics
needs less components and the EMC characteristics and the possible cable length is much longer.
are much better.
Output circuit and recommended input circuit
9081
+5V +5V
Data +
Z
+5V Data -
RS485 Transceiver
RS485 Transceiver 10k
z.B. MAX 490
Clock +
120 Z
Clock -
10k
Z = 120 Ohm

Data transmission SSI
t 1 = T / 2
t 2 < 1 / (4 x fmax)
t 3 = Monoflop time (see below)
n = Resolution in bit
1/ f max ) T ) 1 / f min
f min = min. clock rate (see data sheet)
f max = max. clock rate (see data sheet)
At rest, the clock and data lines are at a high level. After the last positive-going clock-pulse edge the
With the first falling clock-pulse edge, the current data line will remain for the duration of the monoflop
encoder data are stored in the buffer ready to be time t3 at a low level, until the encoder is ready for
sent. With the next rising clock-pulse edge, the data a new data word. The clock line must stay high for
are transmitted bit by bit, starting with the MSB. The at least as long, and then can begin a new read-out
transfer of a complete data word requires n+1 rising sequence again with the next falling edge.
clock-pulse edges (n=resolution in bit), e.g. 14 clock
signals for a complete readout of a 13 bit encoder.

Please note!
Only for type 5850, 5870 and 9081: Only for the new Sendix absolute encoders:
The updating of the data occurs synchronously with The updating of the data occurs immediately with
the read-out cycle. So, the data are as up-to-date as the first falling edge of the clock signal. The data
the interval time between two read-outs. are thus always up-to-date. If a repeated read-out
A periodic read-out of the encoder in the application of the same data word is desired, then a new clock
sequence must be started within the time interval
is therefore recommended, using appropriately
short cycle times, so that current position values are t 3 . If the clock sequence is terminated before the
necessary number of clock pulses, needed for
constantly maintained. It is not possible to read out
the same data word several times. a complete readout of the data word, has been
transmitted, then after a further time interval t 3 the
Monoflop time of the encoder: t 3 = max. 40µs
data line will go high again and signal that the last
read-out sequence has been aborted. It will also
indicate that it is ready for a new data word to be
sent. Monoflop time of the encoder: t 3 = see data
sheet.

© Fritz Kübler GmbH, subject to errors and changes. 02/2015 www.kuebler.com 27