Epson A794-D100 - Manual (Page 42)

Chapter 5: Communication Interface A794 Owner’s Guide
March 1999 36
XON/XOFF Protocol
The XON/XOFF characters coordinate the information transfer between the printer and
the host computer. The printer sends an XON character when it is ready to receive data
and it sends an XOFF character when it cannot accept any more data. The software on
the host computer must monitor the communication link as shown in the following
flowchart in order to send data at the appropriate times.
If XON/XOFF has been selected, the printer also toggles the DTR signal, as described in
the next section, but it does not look at the DSR signal to transmit data.
XON character = hexadecimal 11.
XOFF character = hexadecimal 13.
DTR/DSR Protocol
The DTR signal is used to control data transmission to the printer. It is driven low when
the printer is ready to receive data and driven high when it cannot accept any more
data. Data is transmitted from the printer after it confirms that the DSR signal is low.