User Manual

Energy management
M-Bus Communication Protocol for EM24 M1
5
Check Sum 1 byte
Check Sum: is the arithmetical sum (without carry)
starting from Control Field to the MDH Field (if present,
otherwise the last Data byte)
Stop 1 byte 16h
NOTE: each transferred measurement requires: DIF, DIFE (optional), VIF, VIFE (optional) and Data (2 or 4 Byte). See also Table
1
The device supports the FCB/FCV-bit transfer protocol. This mechanism is activated if the FCV-bit is
set to one in the Request Frame generated by the Master, otherwise the mechanism is ignored by the
Slave. The FCB/FCV protocol allows a safer transfer from Slave to Master when the Slave response has
more than one Long Frame. After a SND_NKE Procedure, the Master transmits in the REQ_UD2 
RSP_UD a Control Field with FCB-bit set to one (Control Field = 7Bh) and the Slave will reply with the
first Long Frame. If this data is correctly received from the Master, the Master itself will send to the Slave
a new Request Frame with the FCB-bit cleared (Control Field = 5Bh), hence the Slave will send the next
Long Frame. On the contrary, if the Master did not correctly receive the first Long Frame from the Slave,
it can send to the Slave the Control Field = 7Bh another time, in this way the Slave will repeat the First
Long Frame. The same is valid for the Second Long Frame. The last Long Frame transmitted by the
Slave does not have the MDH Field, this absence has to be interpreted by the Master as the receipt of
the last Long Frame from the Slave. After a SND_NKE procedure, the slave is always set on the first
frame, even if the last transmitted frame was not the last.
“Version” Field, which is directly read from the device, gives the instrument version:
“Version” Field
HEX
“Version” Field
DEC
Device
5Ah 90 EM24DIN M1 (all models)
The meter supports the “secondary address” addressing and its research through the wild card.
The latter corresponds to the nibble “Fh” and can substitute one BCD digit of the secondary address so
that, during the slave’s selection, it can be ignored. It is so possible to address groups of slaves whose
secondary address is the same except for the wild card. An appropriate algorithm allows the master to
identify all slaves among those present in the network.
The sub unit function allows to mark electrical variables with the same engineering unit (for example:
Wsys, WL1, WL2 and WL3 whose engineering unit is Watt). The meter supports the sub-unit, Please,
give a look at Table 2
1.2.3 Reset Function
This function code is used by the Master and resets the Slave. After a Reset, the FCB/FCV-bit
mechanism is re-initialized. Also, a Primary Data Request is automatically de-selected.
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 50h Application Reset Code
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