Filter
Top Products
CHAPTER 3
Communication Channels
54 Communication Dynamics
XON/XOFF Flow Control for PC Communication 3
To set up the LaserWriter Select 310 printer for serial interface with the IBM PC over the
serial port using XON/XOFF flow control at 19200 baud, issue the following MS-DOS
commands to your computer:
MODE COM1:19200,N,8,1
MODE LPT1:=COM1:
These commands alone are not sufficient to handle XON/XOFF flow control. Some
applications may handle this protocol themselves. Otherwise, you should install a
different MS-DOS printer driver to avoid communication problems when printing large
documents.
Note
You must issue these commands to your IBM PC whenever the computer
is turned on. Alternatively, you may place them in
the AUTOEXEC.BAT file on your MS-DOS disk.
◆
The LaserWriter Select 310 printer comes from the factory with its serial port configured
for option 68: 8-bit data, no parity, DTR flow control, with 57600 baud. If you need to set
up the printer for XON/XOFF communication at 19200 baud, send the following routine
to the printer from the host, using either the parallel port, or the serial port at 57600 baud.
serverdict begin 0 exitserver
statusdict begin
9sccbatch 0 eq exch 19200 eq and not
{9 19200 0 setsccbatch} if
end stop
This routine tests the current values of the sccbatch parameters (see Chapter 2), and if
they are not set for 19200 baud and option 0, it sets these values using setsccbatch.
Note
These changes are not permanently stored, since the LaserWriter Select
310 printer has no EEROM. They will not persist across power cycles.
You should send this sequence each time the printer is turned on or
whenever the serial communication parameters have been changed. ◆
Communication Dynamics 3
Data transmitted by the LaserWriter Select 310 printer, whether it is generated by
executing the PostScript language program or by some other spontaneous event such
as an error, is logically asynchronous with respect to the data received. This means that
the host computer must be prepared to consume data received from the LaserWriter
Select 310 printer while waiting to send more data to the printer. If the host computer is
not set up to do this, the printer and the host may each wait for the other to consume
data, and a deadlock will occur.