28 •
PROFIBUS
Fieldbus Dependent I/O Module
PROFIBUS DP
A diagnostic bit DSx covers a group fo 4 outputs.
diagnostic bit
Corresponding output group
DS1
DO1 ... DO4
DS2
DO5 ... DO8
DS3
DO9 ... DO12
DS4
DO13 ... DO16
The diagnostic status bit is set to '0' when the status of an output does not co-
incide with the status read back internally.
Valid reasons for the activation of a diagnostic message:
•
Missing voltage supply to the output drivers
•
Short circuit of an output conductor
•
Overload at the output
•
Internal fault of an output driver
A diagnostic status bit is set if a transmitted value of '1' by the master control-
ler does not produce a threshold voltage at a corresponding output.
When such a fault is detected, the electronic module transmits a periphery
fault signal to the fieldbus controller board, and illuminates the
“OVERLOAD” LED. The I/O module switches the LED off again once the
fault has been corrected, and after a 1 second delay, cancels the periphery fault
message.
7.6 Process Data Image
The Process Data Image is divided into the input and the output image.
Abbreviation
Description
DIx
Status of the Digital Input „x“
DOx
Status of the Digital Output „x“
Byte 0 (in)
1. Byte of the I/O Module in the Input Process Image
Byte 1 (in)
2. Byte of the I/O Module in the Input Process Image
Byte 0 (out)
1. Byte of the I/O Module in the Output Process Image
Byte 1 (out)
2. Byte of the I/O Module in the Output Process Image
.x
Bit position in the byte
