Printronix SLPA7000 User Manual page 220

Chapter 5
Communications Failures
Device Handshaking
Handshaking is the exchange of signals between the host computer and the
printer to indicate the status of the data being transferred. In serial data
transfer the printer uses both hardware and software handshaking and
transmits both forms simultaneously when the input buffer is full.
The printer can be used with either serial or parallel host interfaces. Parallel
interfaces are usually straightforward, with no special settings required. Serial
interfaces, however, have a variety of possible communication parameter
settings.
There are two methods of handshaking on a serial interface:
•
Hardware Handshaking
This is an electrical signal controlled by the logic state on pin 20 of serial
interface connector J2 at the back of the printer. The signal goes high
when the printer is ready to receive data. The signal goes low when the
printer is in the busy state, which indicates that the input buffer is full and
can no longer receive data.
•
Software Handshaking
XON and XOFF are software signals that control serial data flow between
the printer and the host system. When the printer input buffer is full, the
printer sends the XOFF (Hex 13) character, which signals the host to stop
sending data. When space becomes available in the input buffer, the
printer sends the XON (Hex 11) character, which tells the host that the
printer is ready to receive more data.
The Printer Interface
The printer will not function properly if an incorrectly wired interface cable or
the wrong interface cable is installed.
When the printer is first powered up, it resets itself to the following default
communication parameters:
Use the SERIAL PORT menu to change serial interface parameters. (Refer to
the User's Manual .)
220
PARAMETER DEFAULT VALUE
Baud
Data Bits
Parity NONE
Stop Bits
9600
8
1