Modbus TCP server
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COM465IP-COM465DP_D00216_02_M_XXEN/03.2017
6.2.4 Reference data records of the process image
To make it easier to check the configuration and the Modbus TCP data access to devices, the
COM465… provides a reference data record at the virtual address 0.
Special features of the Modbus communication are the byte offset and the word and byte order in
the memory (Big Endian). At the end of this chapter, a few examples of correct configuration are giv-
en, which might be helpful.
6.2.4.1 Address assignment of the reference data record
As shown in the following table, the Modbus start address for access to the reference data record is
derived from device address 0.
Tab. 6.3: Start addresses for the reference data record query
The start addresses provide the following reference values:
0x0000: TEST (device type)
0x000E: 1 (common alarm, LSB of the high byte is set)
0x0010: 230 V undervoltage (reference value on channel 1)
0x0014: 12.34 A overcurrent (reference value on channel 2)
6.2.4.2 Reference value on channel 1
The following reference value is stored in this channel: 230.0 V undervoltage
Tab. 6.4: Reference data stored in channel 1
No real device can have address 0!
Address 0 only serves to simulate data access.
Word
Virtual
device address
HiByte
LoByte
00 0E 10 14
0
HiByte
0x00
Device type
Common
Alarm
Channel 1 Channel 2
Word 0x10 0x11 0x12 0x13
HiByte LoByte HiByte LoByte HiByte LoByte HiByte LoByte
0x43 0x66 0x00 0x00 0x00 0x04 0x00 0x4D
Floating point value AT&T R&U Description
230.0 No/No Volt Undervoltage
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