Parameterizing and diagnosis functions for all bus couplers
PCD0
26/766 E2
(HB_PCD0 26 766_E2.DOC)
SAIA-Burgess Controls Ltd.
Page 145
10.2
Data structure
Parameterizing and diagnosis data is always mapped on the first 2
words (4 Byte) of output data (PLC --> bus coupler) and the first 2
words (4 Byte) of input data (bus coupler --> PLC).
Diagnose Output
Diagnose Input
Byte 3
Byte 2
Byte 1
Byte 0
Byte 3
Byte 2
Byte 1
Byte 0
EC/BC
FC
FC
Byte 3
Byte 2
Byte 1
Byte 0
Byte 3
Byte 2
Byte 1
Byte 0
FC
FC
EC/BC = EC / BC bus coupler
Byte 0 of Diagnose Output and Diagnose Input is always reserved for
the function code (FC).
Diagnose Output
Diagnose Input
Byte 3
Byte 2
Byte 1
Byte 0
Byte 3
Byte 2
Byte 1
Byte 0
EC/BC
FC
FC
10.3
Sequence
The PLC initiates a function by sending the relevant function code to
the bus coupler in byte 0 of diagnose Output. The bus coupler
executes the function within one bus or PLC cycle. Once the function
has been processed, the function code is repeated in the bus coupler
response in byte 0 of diagnose Input.
If the master uses the same function several times in sequence,
function 255 (Reset) must be executed in-between. This ensures
correct evaluation of the finished message from the bus coupler.