Printronix T4204 Maintenance Manual page 44

Chapter 3
Communications Failures
Table 3: Common Communications Problems
Problem
Fails to print from host
-or-
Prints incorrect characters
-or-
Prints extra characters
-or-
Drops characters
Device Handshaking
Handshaking is the exchange of signals between a 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. The two methods of handshaking that can be used, hardware and
software, are explained below.
•
Hardware Handshaking
This electrical signal is controlled by the logic state on pin 20 of the 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 printer 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 transmits an XOFF (CTRL S) character that signals the host to
stop sending data. When memory space becomes available in the input
buffer, the printer sends an XON (CTRL Q) character, which tells the host
that the printer is ready to receive more data.
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Interface
parallel - Interface cable defective
- Host/Network configuration
- Printer logic
- Terminating Resistors
serial - Host/Printer interface cable pinouts incompatible
- Host/Printer/Network configuration
- Set DTR and RTS bothTrue
- Interface cable defective
- Printer logic
twinax - Interface cable defective
- Host-Printer definition
- Controller/Network configuration
- Printer logic
coax - Interface cable defective
- Controller/Network configuration
- Printer logic
Common Causes