Asynchronous Terminals and Printer Processes Programming Manual

PRINTER PROGRAMMING CONSIDERATIONS
Error Handling
to output a console message. The DEVICE POWER ON error is
returned to the application if this request is not the first
request made after the device was opened.
When the 5530 goes offline because of a paper out, cover open, or
other recoverable condition and then goes back online, it prints
the contents of the buffer. The printer then waits for more
data. If error 104 has occurred, the operator should reset the
top of form and print the job again.
DATA PARITY Error
If a parity error is detected in data going to the printer or
in status returning from the printer, the I/O process attempts
to recover unless the parity error persisted after the retry
count was exhausted. A parity error that occurs while the device
is offline (such as DEVICE NOT READY or PAPER OUT) will be
recovered.
The Cut-Sheet Feeder
The 5530 can be equipped with a cut-sheet feeder instead of a
tractor feeder. When the cut-sheet feeder is installed, the
paper-out sensor for continuous forms does not work. The paper
out condition is not detected until after a print request is
issued. The printer spends several seconds trying to cycle paper
through the feeder before the paper-out condition is detected.
When the cut-sheet feeder is installed, the MICRO-LINE button on
the printer is disabled.
PROGRAMMING CONSIDERATIONS FOR DTR-TYPE PRINTERS
DTR-type printers include the Tandem models 5540 and 5541 and
various printers from other manufacturers. These printers all
use DTR flow control. The printers manipulate the state of
the data terminal ready (DTR) signal. The following example
illustrates how DTR flow control works.
November 1987 7-19