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29 COM461MT_D00011_00_M_XXEN/05.2013
7. Modbus process image in the memory of the
COM461MT
The device holds a process image in the memory. This image represents the
current statuses and values of up to 150 BMS devices for each monitored in-
ternal BMS bus.
7.1 Requesting data
7.1.1 Modbus function code
The memory in the COM461MT can be read using the Modbus function 4
"Read input registers". The volume of the data requested depends on the
number of bytes selected in the Modbus client used. Up to 125 words (0x7D)
can be read with a single request. An individual addressable byte, such as the
set bit for a stored common alarm, can also be read.
7.1.2 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
Not used 0x96FF 0xFFFF 0x6900
For some Modbus clients an offset of 1 must be added to
the register addresses. Example: process image start ad-
dress = 0x0101.