Modbus Examples To Read Out Data; Reference Data Records Of The Process Image - Bender COMTRAXX CP9 Series Manual

Modbus TCP server

4.2.3 Modbus examples to read out data

Example: Reading out from ATICS channel 1 (voltage line 1)
CP9xx has address 1 in subsystem 1. ATICS channel 1 of internal address 3 is to be read out. The content is the
voltage of line 1 as floating point value.
Modbus request:
00 01
00 00
00 06
01
04
03 10
00 02
Response:
00 01
00 00
00 05
01
04
04
01 00 43 63
00 04

4.2.4 Reference data records of the process image

To make it easier to check the configuration and the Modbus TCP data access to devices, the CP9xx provides a
reference data record at the virtual address 0.
Adress „0"
No real device can have address 0!
Address 0 only serves to simulate data access.
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 given, which might be hel-
pful.
4.2.4.1 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.
Virtual
Device address
0
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)

CP9xx_D00349_07_M_XXEN/01.2020
00 01 00 00 00 06 01 04 03 10 00 02
Transaction ID (is generated automatically)
Protocol ID
Length
Unit ID (subsystem 1)
Modbus function code 0x 04 (read input registers)
Start register
(Register address at which the value in the memory image appears: 784 = 0x 03 10)
Length of the data (words)
00 01 00 00 00 06 01 04 04 01 00 43 63 00 00
Transaction ID (is generated automatically)
Protocol ID
Length
Unit ID (device address of the CP9...)
Modbus function code 0x 04 (read input registers)
Length of the data (bytes)
Data floating point value (0x 43 63 01 00 (words swapped) = 227.0039)
Alarm and test type (00 = no alarm), range and unit (04 = volts)
Word
LoByte
HiByte
00
HiByte 0x00 Device type
Tab. 4.3: Start addresses for the reference data record query
0E 10
Common alarm Channel 1
14
Channel 2
29