Festo ELGL-LAS, Operating Instructions Manual

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FESTO ELGL-en 0904NH
6.7 Displacement encoder for BiSS interface
The BiSS interface is a 2-wire interface for interference-immune sensor connec-
tion. In contrast to the SSI interface, the data transmission is bi-directional,
which means, for example, that data can also be written into the sensor for pa-
rametrisation.
Data is transmitted via a pulse cable controlled by the master and a data cable
controlled by the sensor as serial transmission. Data is written to the slave via
the cycle's pulse width modulation in accordance with the "BiSS B mode" pro-
tocol specification http://www.biss-ic.de/files/BiSS_b3ds.pdf; the direction of
the data cable is not switched. Pulse and data are transmitted using RS485
technology, which means a signal is sent not-inverted as well as inverted and
issued at the receiver as differential input. This suppresses common-mode in-
terference. The data are also secured by a CRC code.
The BiSS interface supports 2 read-out modes:
- The sensor data channel for fast pulse out (pulse up to 10 MHz) of the sen-
sor information
- The parameter channel for reading and writing sensor parameters as well as
for depositing user-specific data protected against zero voltage in the sensor's
EEPROM
The distinction is made on the basis of the start bit, details can be referred to
in the specifications given.
Fig. 29: Sensor data communication
Bits Type Label
0…8 DATA Cycle counter P(7:0);
0…8 bit (multiturn posi-
tion)
3…13 DATA Angle data S(12…0);
3…13 bit (singleturn
position)
1 Error Error bit E0
(amplitude error)
1 Error Error bit E1
(frequency error)
5…6 CRC Polynomial 0x25
x
5
+x
2
+x
0
(inverted bit
output)