BEL DIGITAL AUDIO
BMA2-4SHD
BM-A series serial protocol
2006 BEL (Digital Audio) Ltd
22
Version 0.8
B
B
M
M
-
-
A
A
s
s
e
e
r
r
i
i
e
e
s
s
s
s
e
er
i
i
a
a
l
l
p
p
r
r
o
o
t
t
o
o
c
c
o
o
l
l
Overview
Commands to be communicated to remote BM-A series units are arranged in frames. These
frames will then be sent to the remote unit, which will always reply with either ACK for
acceptance or NAK for rejection. Any requested reply then follows in the same frame format.
Frame format
The frame starts with a start character 0xAA (alternating ones and zeros). This is followed by
the destination address, the source address, the command code, the data count, the data, a
checksum and an end flag 0xFE.
Start Flag 0XAA
Destination Address
Source Address
Command
Data Count
Data
Checksum
End Flag 0XFE
Start Flag:
The start flag 0XAA may be sent at any time. If sent during a frame this will cause the frame
to effectively restart.
Destination Address:
This should be set to 1.
Source Address:
This should be set to 1.
Command:
This character is the command for the remote unit and must fall in the range 0X80 to 0XEF.
More details of the relevant codes are shown below.