Modbus Address Structure For Bms Devices; Modbus Process Image In The Memory Of The Cp9Xx; Querying Data - Bender COMTRAXX CP9 Series Manual

4.1.5 Modbus address structure for BMS devices

Function
Device type
Timestamp
Common alarm
No BMS bus con-
nection
Unused
Channel 1...32
Alarm and test
Channel 33...64

4.2 Modbus process image in the memory of the CP9xx

The device holds a process image in memory. This image represents the current states and values of all devices
that are in the same system as the CP9xx

4.2.1 Querying data

4.2.1.1 Modbus function code FC03
The parameters and measured values of all devices in the subsystem can be read using the Modbus function
0x03 "Read Holding Registers". This is only possible on the subsystem level, not in the entire system. The unit
ID refers to the respective device address.
4.2.1.2 Modbus function code FC04
The process image in the memory of the CP9... can be read using the Modbus function 4 "Read Input Regis-
ters". Device name, device channel states and alarm and operating messages can be accessed via this function.
This is possible for all devices in the system. Here, the unit ID refers to the subsystem address.
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 word can also be read, for example, to detect the set bit for a saved common alarm.
4.2.1.3 How are the memory areas organised?
Memory utilisation
Reference values
for test purposes
Process image
Unused
For 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 for one subsystem is described
below. Please refer also to the "BCOM" manual, which provides information about the entire addressable sys-
tem.
22
Address range Number of bytes
0x00...0x09 20 bytes
0x0A...0x0D 8 bytes
0x0E (high byte) 1 byte
0x0E (low byte) 1 byte
0x0F 2 bytes
0x10...0x8F 32 x 8 bytes
0x90...0xFC 218 x 8 bytes
Start address End of memory area
0x0000 0x00FF
0x0100 0x95FF
0x96FF 0xFFFF
Modbus TCP server
Number of
words
10 words
4 words
0.5 words
0.5 words
1 word
128 words
109 words
Size of memory area
0x0100
0x9500
0x6900
CP9xx_D00349_07_M_XXEN/01.2020