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SW-BA-e-2020
5.2 Transmission protocol
The RS-232 interface protocol for
SW 1000/200 is
based on a blockwise transmission
according to the following pattern
A typical command block or response block consists of a start character, the ID, the
attribute character, the command or data, the end character, the block check character,
the carriage return and carriage return characters, as shown in the following figure:
<STX>
ID
ATTR
Command or data
<ETX>
BCC
<CR>
<LF>
5.2.1 Starting and stopping blockwise transmission
A command block or response block contains the start characters, end characters, and
other control characters as shown in the following figure
Name
Hex
Meaning
<STX>
02H
Start sign
<ETX>
03H
Stop sign
<CR>
0DH
Carriage returns
<LF>
0AH
Line feed
5.2.2 Device ID
Each command block contains an ID. It is used to distinguish between several sound
level meters in a network. When the sound level meter receives a command block, it
compares the ID in the command block with its own ID. If both match, the
corresponding operation is performed. If not, the command is ignored. The response
block returned by the sound level meter also contains the ID indicating who sent the
block.
☆
Note : Make sure that
the IDs of the sound level meters in the same network are
different, otherwise operation will be disturbed!
The ID is a byte of the binary address. The range is between 1 and 255, the
corresponding hexadecimal value is 01H to FFH.
This means that the command is a broadcast command if the ID is contained in the
command block 00H. The sound level meter executes the instruction independently of
its own ID without data return if the command is a broadcast command.
Name
Hex
Meaning
ID
01H to FFH
Device ID
00H
Broadcast command
5.2.3 ATTR attribute characters
The ATTR attribute character specifies the type of command or response.