Function description
Operating Manual PSSu E S ABS SSI(-T)
21441-EN-05
13
}
Data format:
The data format in which the module transmits the position data of the connected abso-
lute encoder to the head module.
– Gray code (default)
– Binary code
The position data is transmitted to the head module via the ST module bus with 4 Bytes, ir-
respective of the configured input data length. The module sends additional status informa-
tion.
Timing diagram: Example of SSI data transfer
:
Cl
D
a
b
d
e
c
Legend:
The bit width in the example is 6. The position of the encoder is 001101 in gray code, i.e.
9
D
.
}
a: Data transfer begins with a falling edge at the Cl signal.
}
b: The first bit is transmitted with the first rising edge from the Cl signal.
}
c: The time up to the second rising edge is the period length T. 1/T is the signal fre-
quency.
}
d: The last rising edge from the Cl signal ends the transfer. The encoder acknowledges
the end of the transfer with a 0 signal.
}
e: The encoder can transfer data again as soon as there is a 1 signal at input D.
4.2.2
Integrated protection mechanisms
When the PSSu E F PS1(-T) or PSSu E F PS2(-T)(-R) is used to supply the system, the
module supply is buffered for 20 ms if the supply voltage is interrupted.
The module detects the following errors:
}
Start-up error
}
Configuration error
}
ST communication error
}
Bus termination error
