COM462RTU_D00010_04_M_XXDE / 06.2021 21
COMTRAXX® COM462RTU
6
Modbus process image in the memory of the COM462RTU
The device holds a process image in memory. This image represents the current statuses and
values of up to 150 BMS devices for each monitored internal BMS bus.
6.1
Querying data
6.1.1 Modbus function code
The memory in the COM462RTU can be read using the Modbus function 0x03 (Read Holding
Registers). The volume of the queried data depends on the number of bytes selected in the
Modbus client used. Up to 125 words (0x7D) can be read with a single query.
An individual addressable byte, such as the set bit for a saved common alarm, can also be read.
6.1.2 How are the memory areas organised?
Memory utilisation
Start address
End of memory area
Size of memory area
Reference values
for test purposes
0x0000
0x00FF
0x0100
Process image
0x0100
0x95FF
0x9500
Unused
0x96FF
0xFFFF
0x6900
i
In some Modbus clients, an offset of 1 must be added to the register addresses.
Example: process image start address = 0x0101.
The assignment of the memory addresses and the associated memory content is described
below.
