Denso BHT-7500W, BHT-7500S user manual Basic Format of Transmission Messages

Chapter 3. Communications Operations of the BHT

[ 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 Data text 1 Data text 2

Data text n

Transmission

Message

S		E	B
O	Heading text	T	C	Transmission block
H		X	C

S	Serial		E	B
T	number	Data text 1	T	C	Transmission block
X	(5 bytes)		X	C

S	Serial		E	B
T		Data text n	T	C	Transmission block
	number
X			X	C

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 ].

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