| Starts the |
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| Sends an <ENQ> | ||||
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| Sends <ENQ> |
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| Receives status signal. | |||
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| Receives status byte. |
| Receives a check byte. |
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NO | Is the data buffer |
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| Is the status an | YES | ||
| empty? |
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| error? |
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| YES |
| Horizontal | NO |
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| Sends <STX> |
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| parity check |
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| Is an odd parity | NO | Check byte = | NO | |
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| check? |
| test byte? |
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| YES |
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| YES |
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| (FF) H is set for the text | The test byte is set at (0)H. | Sends <ETX> |
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| byte. |
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| (Printing) |
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| Sends <CAN> |
| Acquires the exclusive OR of the content |
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| of the text byte and the data to sent, then |
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| it is used as the content of the test byte. | Ends the |
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Transmits the data to the printer.
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| Is there a data block in | NO |
NO |
| the |
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Is this the last data in
a block?
YES
YES
RET
Check byte:
Horizotal parity of the printer. Test byte:
Horrizontal parity of the host computer.
STX-ETX mode flow diagram for host computer
– 21 –
