57
Name
Hex
Meaning
‘
C
’
43H
Command Block
‘
A
’
41H
Response Block
<ACK>
06H
Normal Response
<NAK>
15H
Error Response
5.2.4 BCC (Block Check Character)
BCC check bit which include in block is calculated by the sender. The receiver can calculate
the block’s BCC value and will compare with the BCC value contained in the send block. If
same, it indicates that the received block is correct. BCC value is calculated by using bytes
between <STX> and <ETX> with XOR operation. Sound level meter will not verify operation
and directly authorized instruction if BCC is 00H.This way you can simplify the sending of the
instruction block, but do not recommend this way for long-distance applications, because the
BCC is the only way to guarantee reliability of data transmission.
Name
Hex
Meaning
BCC
01H~FFH
XOR Checksum
00H
Ignore the Checksum
5.2.5 Block Transfer Format
Block transfer of data have four types: command block, response block, normal response
block and error response block. The following were to describe the four types of instruction
format.
(1) Command Block: sent by the computer.
<STX>
ID
ATTR
Instruction Parameter
<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 included, all parameters should
be separated by spaces.
(2) Response Block: sent by the sound level meter.
<STX>
ID
ATTR
Response
<ETX>
BCC
<CR>
<LF>
1
1
1
N
1
1
1
1
Byte
Byte
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