DSC fieldbus modules
8540467 • 28/03/2019 • Rev.2 9
DESCRIPTION
The MBx communication module gives access to various information related to the DSC
system and allows to send commands from the PLC.
Each device connected to the DSC inputs is characterized by an ON/OFF status and a
possible diagnostic. The processing of the inputs according to the program loaded on
the DSC generates the ON/OFF status of the safety outputs which can also have
diagnostics.
PROCESS IMAGE
System status and I/O status are available on the cyclic process image, while I/O
diagnostics, system errors and the M1/M1S program CRC are accessible as acyclic data.
The process image has a fixed size with subsections for each information group: there
are sections showing the status of the DSC inputs, the status of the safety outputs, the
status of the probes and, if the dedicated module is present, the value of the analogue
measures.
The Fieldbus inputs allows the PLC to cyclically send up to 32 ON/OFF status and are
used as unsafe inputs in the DSC program.
The System status bits are described as follows:
1. Bit 0: present DSC presence
2. Bit 1: present diagnostic presence
3. Bit 2: error presence
The acyclic sections for diagnostics or errors report significant data if the relative bit is
present in the status byte.
The section dedicated to the input status has a size of 16 bytes and allows to know the
status of up to 128 inputs. The priority order of the modules is as follows:
•M1/M1S, MI8O2, MI16, MI8, MI12, MV2, MV1, MV0, MI8O4.
The section dedicated to the safety outputs status has a size of 4 bytes and allows to
know the status of up to 32 outputs. The priority order of the modules is as follows:
•M1/M1S, MI8O2, MO2, MO4, MOR4, MOR4S8, MO4LHCS8, MI8O4.
If two or more modules of the same type are installed the one with the lowest node
number is shown first.
Each module with inputs has a number of bits corresponding to the number of physical
inputs; thus modules M1/M1S, MI8, MI8O2, MI8O4 will use 1 byte and modules MI12T8
and MI16 2 bytes. Modules MV0, MV1 and MV2 uses 1 byte each.
The status of the probe is represented with 4 bytes.
In fieldbus where the allocation is important (e.g. PROFIBUS, PROFINET), the Fieldbus
input bytes must be mapped before the bytes in output.
If there is a fieldbus module in the DSC system, DSDESIGNER will include in the report a
table with the I/O index for all inputs, fieldbus inputs, probes and safety outputs in the
circuit diagram.
For the process data mapping description for your fieldbus please refer to the
Addendum1: “Process data mapping for MBx Fieldbus expansion modules” annex at
the bottom of the present manual.
