Bender B95061094, Installation Manual

Page: 25 / 44

Modbus TCP server
25 CP9xx-Kit_D00399_00_M_XXEN/07.2019
5.2.2 Memory scheme of the process image
5.2.2.1 Structure of the process image
As illustrated in the table, the Modbus start address for the respective process image is derived from the device
address. 256 (0x100) words or 512 bytes are reserved for each device. They contain all the information reques-
ted and transmitted from the bus.
Tab. 5.1: Modbus start address for each device for which a request can be sent.
5.2.2.2 Memory scheme of an individual device
Devices can feature various types of analogue and/or digital channels. Please take into consideration that there
are device-specific differences:

BMS devices usually feature 12 channels

MK800/TM800 supports up to 64 digital channels in the master mode

The channels 33 to 64 transmit digital messages only
Use the tables on Seite 25 and Seite 26 to determine the start address to request the following device parame-
ters:

Device type

Timestamp

Common alarm

Device error

BMS channel
Example:
Channel 2 of the device with address 3 is to be queried. How is the start address determined for querying the
channel? In our example, the relevant cells in the table are marked bold.
1. For device address 3 the first part of the address, 0x03 (high byte), is taken from Tabelle 5.1.
2. For channel 2 the second part of the address, 0x14 (low byte), is taken from Tabelle 5.2. For the number
of words to be requested the number 4 is taken from the same table:
(0x14 to 0x17 = 0x04).
3. The start address 0x0314 is formed from the high byte and low byte.
Modbus address ranges of the process images in the memory
Device address
Word
HiByte LoByte
00
…
FF
1 0x 01 Device 1
2 0x 02 Device 2
3 0x 03 Device 3
… … …
32 0x 20 Device 32
… … …
255 0x FF Device 255
Memory image of a device
LoBy
te
0 1 2 3 4 5 6 7 8 9 A B C D E F
0x 0 --------------------------- Device type ---------------------------- ------ Timestamp ------ C D R.
0x 1 Channel 1 Channel 2 Channel 3 Channel 4
0x 2 Channel 5 Channel 6 Channel 7 Channel 8
0x 3 Channel 9 Channel 10 Channel 11 Channel 12
0x 4 Channel 13 Channel 14 Channel 15 Channel 16
0x 5 Channel 17 Channel 18 Channel 19 Channel 20