User manual

APOS Premium Printer Series User Manual Page 29 /136 Reference: FDE 3107312 Issue A
4.6 Communication Interface Control
4.6.1 RS232
The RS-232C interface uses either XON/XOFF (software) or DTR/DSR (hardware) protocol to control the
flow of information between the computer and the printer.
In XON/XOFF mode, a particular character is sent back and forth between the host and the printer to
regulate the communication.
In DTR/DSR mode, changes in the DTR/DSR signal on the RS-232C interface controls the information
flow.
4.6.1.1 XON/XOFF Protocol
The XON/XOFF characters controls 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.
4.6.1.2 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.
Was an XON or
XOFF character
last received ?
Wait for XON
characte
r
Send Data
XON
11 HEX
XOFF
13 HEX
Is DTR
HIGH or LOW
Wait for DTR
To
g
o LOW
Send Data
LOW
HIGH