ABB A43 User Manual page 194

Communication with M-Bus
Request/Respond
When the meter has received a correct telegram it waits between 35 and 80 ms
before it responds. A telegram is considered as correct if it passes the following
tests:
The time between a response from the meter and a new message from the master
must be at least 20 ms.
Send/confirm SND_NKE is used to initiate communication with the meter. When the meter
has received an NKE followed by a REQ_UD2 (see description below), the 1st
procedure
tele-gram from the meter is sent out.
If the meter was selected for secondary addressing it will de deselected. The
value of the FCB is cleared in the meter, i.e., the meter expects that the first
telegram from a master with FCV=1 contains an FCB=1.
The meter can either confirm a correct reception with the single character ac-
knowledge E5h), or it can omit confirmation because it did not receive the
tele-gram correctly.
SND_UD is used to send data to the meter. The meter either confirms reception
of a correct message or it omits confirmation because it did not receive the tele-
gram correctly.
Request/respond REQ_UD2 is used by the master to request data from the meter. RSP_UD is used
by the meter to transfer data to the master. The meter indicates to the master that
procedure
more data will follow in the next telegram by sending 1Fh as the last user data.
If the meter does not respond to the REQ_UD2, it's an indication that the
message was not received correctly or that the address does not match.
A43/A44
User Manual
REQ/RSP
• Start /Parity /Stop bits per character
• Start /Check Sum /Stop characters per telegram format
• In case of a long frame, the number of additional characters received match
the L-field (= L Field + 6).
• If the received data is reasonable
194 2CMC48001M0201
Revision: C