Lexmark Printer manual XON/XOFF Protocol Timing RS-232C

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XON/XOFF Protocol Timing (RS-232C)

Interfaces

When you select this data flow control protocol, the printer sends an XOFF signal when it detects the following BUSY conditions:

•

•

•

Buffer full

Attendance error

Printer not in ready state

The following diagram illustrates XON/XOFF Protocol Timing.

1

RTS

DTR

2

DSR

3

Receive Data Valid

XON XOFF XON

XMT

4

RXD

Legend:

56

1The RTS signal is driven active as long as power is supplied to the printer.

2The DTR signal becomes active at the completion of initialization.

3The printer considers data received invalid when DSR is low and discards the data. (This is conditional depending on the setting of Honor DSR.)

4After you power on the printer and DTR is active, the printer sends an XON signal to the computer (DC1 control or X'11'). However, the computer does not need to detect this initial XON before sending data to the printer, because the printer can be powered on before the computer or terminal.

5The printer sends an XOFF signal (DC3 control or X'13') to request that data transmission end until the buffer clears. About 640 free bytes remain in the buffer at this time. If the computer continues to send data after the printer sent an XOFF signal, data could be lost.

6The printer sends an XON signal to the computer when the buffer space is again available. The serial interface is ready to receive more data.