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
Text | Heading text | Data text 1 | Data text 2 |
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Data text n
Transmission
Message
S |
| E | B |
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O | Heading text | T | C | Transmission block |
H |
| X | C |
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S | Serial |
| E | B |
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T | number | Data text 1 | T | C | Transmission block |
X | (5 bytes) |
| X | C |
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S | Serial |
| E | B |
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T | Data text n | T | C | Transmission block | ||
number | ||||||
X |
| X | C |
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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
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