3 ] Basic Format Of Transmission Messages - Denso BHT-100B User Manual

[ 3 ] Basic Format of Transmission Messages

Basically, the BHT transmits data as units of a file. First, it transmits a heading text
which includes the attribute information of a file (e.g., file name and the number of
data texts) to be transmitted. Following the heading text, it transmits the data text in
the file. A heading text and data text comprise a text.
In actual text transmission, the text is divided into several blocks, then a header and
terminator are added to each block. If the serial number management or error
checking by BCC (Block Check Character) is required, the serial number or BCC is also
added to each block, respectively. This procedure forms a transmission block. A set of
transmission blocks makes up one transmission message.
Shown below is an example of a transmission message formed with the BHT-protocol.
Text
Heading text
S
O
H
S
Transmission
T
Message
X
S
T
X
In the above figure, SOH, STX, and ETX are text control characters as described in [ 2 ]
Control Characters, (2). A serial number is expressed by a five-digit decimal number,
starting from 00001 to 32767, and identifies transmitted data texts. For the BCC, refer
to Appendix B, B.1, "BHT-protocol," [ 3 ].
Chapter 3. Communications Operations of the BHT-100Q/100B
Data text 1
Heading text
Serial
number
Data text 1
(5 bytes)
Serial
Data text n
number
119
Data text 2
E B
T C
X C
E B
T C
X C
E B
T C
X C
Data text n
Transmission block
Transmission block
Transmission block