8 Communication
8.2 Modbus
144
SICAM I/O Unit, 7XV5673, Device Manual
E50417-H1040-C484-A3, Edition 05.2012
8.2.6
Register Assignment
The SICAM I/O Unit uses only holding registers. This is where all messages and commands are stored.
Each Modbus register set has an individual 6-digit identification number.
The holding register set has the identification number 4xxxxx and begins with the register number "1" (400001).
8.2.7
Data Types
The following data types are used for storing variables in the Modbus registers:
•
ASCII string
•
Date/time
•
Indication (read only)
•
Controllable indications (read and write)
•
Commands
NOTE
The following descriptions only quote the last 4 digits of the holding register numbers, for example
0052
for
400052.
NOTE
The data types for Modbus TCP and Modbus UDP (Ethernet) and Modbus RTU (serial) are the same.
NOTE
The storage of variables of more complex data types in the Modbus holding register (that is, variables that are
larger than a holding register) is performed according to the following arrangement:
The register with the lowest address contains the most significant byte (MSB). The register with the highest
address contains the least significant byte (LSB).
MAN_SICAM_IO-Unit_7XV5673_US.book Page 144 Thursday, May 10, 2012 10:59 AM
