E2638_UM_EN. Annex 1. E2638 series Modbus RTU Communication Reference
RS485 communication interface
Databits: 8
Parity: none / odd / even
Stop bits: 1 or 2
Protocol: Modbus RTU
Supported Modbus functions:
03 – read multiple registers
06 – write single register
Communication parameters
Parameter
Permitted values
Default
Supported
baudrates
1200, 2400, 4800, 9600, 19200,
38400, 57600
9600
Data bits
8
8
Parity
none / odd / even
none
Stop bits
1, 2
1
Protocol
Modbus RTU
Modbus functions
03 – read multiple registers
06 – write single register
Error codes
01 – illegal function
02 – illegal data address
03 – illegal data value
04 – slave device failure (details of last error 04
can be read from register 0x0008)
E2638 series Modbus holding registers
Register addresses are shown 0-based, Addr in hexadecimal, Reg in decimal format.
Modbus holding register numbers MHR are shown in decimal 1-based format, and may be addressed either from 00001 or 40001 base.
Addr
Reg / MHR
RW
Description
Supported values (dec)
Default
0x0001
1 / 40002
R
Hardware version
-
0x0002
2 / 40003
R
Software version
-
0x0003
3 / 40004
R
Product serial number
1...65535
-
0x0004
4 / 40005
RW
Slave ID (net address) *
1...247 **
1
0x0005
5 / 40006
RW
Baudrate *
1200, 2400, 4800, 9600, 19200, 38400, 57600
9600
0x0006
6 / 40007
RW
Response delay, ms
1...255
10
0x0007
7 / 40008
RW
Stop bits, parity bit *
1 – no parity bit, 1 stop bit (default after factory reset)
2 – no parity bit, 2 stop bits
3 – odd parity, 1 stop bit
4 – even parity, 1 stop bit
NOTE
: 3 and 4 are available starting from the Software version 0x218 (dec. 536)
1
0x0008
8 /40009
R
Last error code
1...255
-
0x0011
17 / 40018
RW
Restarts counter
write ‘42330’ to restart device
-
* – The new value is applied after restart.
** – Broadcast slave ID 0 can be used to assign a new ID to device with unknown ID. When addressing by ID 0 the device shall be
the only Modbus instrument in the network. The device will not respond to Master command when addressed by ID 0.
*** – This value is dynamic and not kept in EEPROM after restart
