User Manual

Energy management
M-Bus Communication Protocol for EM24 M1
6
1.2.4 Switching Baudrate Function
The Master can set the Slave’s Baud rate to a different value from 300 BAUD as a matter of fact, 2400
and 9600 BAUDs are available. The Slave confirms the correctly received request by transmitting the
E5h character and the old baudrate and uses the new baudrate from now on.
Request frame
Description Length Value Note
Start 1 byte 68h
L 1 byte 03h
L 1 byte 03h
Start 1 byte 68h
Control 1 byte 53h or 73h
Physical Address (Slave) 1 byte 1 to F7h (1 to 247)
CI 1 byte B8h/BBh/BDh B8h = 300 BAUD, BBh = 2400 BAUD, BDh = 9600 BAUD
Check Sum 1 byte
Check Sum is the arithmetical sum (without carry) of
Control Field, Physical Address (Slave) and CI-Field.
Stop 1 byte 16h
Response frame (correct action)
Description Length Value Note
Confirm Character 1 byte E5h
1.2.5 Changing Primary Address
The Master can set the primary address of the Slave. The Slave confirms the correctly received request
by transmitting the E5h character and uses the new address from now on.
Request frame
Description Length Value Note
Start 1 byte 68h
L 1 byte 06h
L 1 byte 06h
Start 1 byte 68h
Control 1 byte 53h or 73h
Physical Address (Slave) 1 byte 1 to F7h (1 to 247)
CI 1 byte 51h
DIF 1 byte 01h
VIF 1 byte 7Ah
New Physical Address (Slave) 1 byte 1 to F7h (0 to 247)
Check Sum 1 byte
Check Sum is the arithmetical sum (without carry) of
Control Field, Physical Address (Slave) and CI-Field, DIF,
VIF and New Physical Address (Slave)
Stop 1 byte 16h
Response frame (correct action)
Description Length Value Note
Confirm Character 1 byte E5h
1.2.6 Primary Data Request (SND_UD)
The Master unit can acquire only a partition of all data stored in the energy module EM24, by specifying
the desired VIF, VIFE in a Primary Data Request procedure. It is possible to program the Slave in order
to obtain one or more measurement up to 20. The slave confirms the request with the E5h character.
From now on, each REQ_UD2  RSP_UD will generate the transfer of the only selected data instead of
all Data Slave. For example, with 08h, FDh, 48h, the Master programs the Slave to obtain only the
Volt*10 Data. With 08h, FFh, 03h only the Hz*10 measurement will be obtained. With the string : 08h,
FDh, 48h, 08h, FFh, 03h both Volt*10 and Hz*10 are programmed. Note that the Data response is