Lexmark C530DN Technical Reference - Page 342

8-26 Interfaces XON/XOFF Protocol Timing (RS-232C) 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 XMT RXD XON 4 XOFF XON 5 6 Legend: 1 The RTS signal is driven active as long as power is supplied to the printer. 2 The DTR signal becomes active at the completion of initialization. 3 The printer considers data received invalid when DSR is low and discards the data. (This is conditional depending on the setting of Honor DSR.) 4 After 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. 5 The 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. 6 The printer sends an XON signal to the computer when the buffer space is again available. The serial interface is ready to receive more data.