SW-BA-e-2020
41
Name
Hex
Meaning
‘C’
43H
Command block
‘A’
41H
Answer block
<ACK>
06H
Normal response
<NAK>
15H
Error response
5.2.4 BCC (block check character)
The block check character bit in the block is calculated by the sender. The receiver
then calculates the BCC value of the block and compares it to the BCC value in the
sender block. If both are identical, it follows that the received block is correct. The BCC
value is calculated from bytes between <STX> and <ETX> using the XOR operation.
When BCC = 00H, the sound level meter does not check the input and directly
executes an authorized instruction. In this way, you can simplify the sending of the
instruction block; however, this procedure is not recommended for long distance
transmissions because BCC is the only way to guarantee the reliability of the data
transmission.
Name
Hex
Meaning
BCC
01H to FFH
XOR checksum
00H
Ignore checksum
5.2.5 Block transmission format
Block transmission of data is possible with four types: as command block, as response
block, as normal response block and as error response block. The four instruction
format types are described below.
(1) Command block: sent by the computer.
<STX>
ID
ATTR Instruction Parameters <ETX>
BCC
<CR>
<LF>
1
1
1
3
N
1
1
1
1
Where: ATTR='C'.
All instructions occupy 3 bytes. If more than one parameter is contained, all parameters
must be separated by spaces.
(2) Response block: Sent by the sound level meter.
<STX>
ID
ATTR
Answer
<ETX>
BCC
<CR>
<LF>
1
1
1
N
1
1
1
1
Where: ATTR='A'.
If there is more than one response data, the data must be separated by ",".
(3) Normal response: Sent by the sound level meter.
<STX>
ID
ATTR
<ETX>
BCC
<CR>
<LF>
1
1
1
1
1
1
1
Where: ATTR=<ACK>
。
(4) Error response: Transmitted by the sound level meter.
<STX>
ID
ATTR
Error code
<ETX>
BCC
<CR>
<LF>
1
1
1
4
1
1
1
1
Where: ATTR=<NAK>.
Byt
e
Byt
e
Byt
e
Byt
e