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,
terminator, serial number, receiver station's ID, and CRC-16 (Cyclic Redundancy Check)
are added to each block. 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-Ir
protocol.
Heading
Text
text
D
L
E
D
L
Transmission
Message
E
D
L
E
In the above figure, DLE SOH, DLE STX and DLE ETX are text control characters as
described in [ 2 ] Control Characters, (2). An ID denotes the ID number of the receiver
station, expressed by two bytes. A serial number is expressed by a five-digit decimal
number, starting from 00001 to 32767, and identifies data texts. For the CRC-16, refer
to Appendix B, B.2, "BHT-Ir protocol, " [ 3 ].
You can use the control characters for expressing IDs, serial numbers, or text data.
Chapter 3. Communications Operations of the BHT-100Q/100B
Data text 1
S I
Heading text
O
•
D
H
(2 bytes)
I Serial
S
number
T
•
D
X
(5 bytes)
S I
Serial
number
• T
X D
Data text 2
D
L
•
E
D
Data text 1
L
•
E
D
Data text n
L •
E
125
Data text n
E C
Transmission
T R
block
X C
E C
Transmission
T R
block
X C
E C
Transmission
T R
block
X C