Apple LaserWriter Select 310 Specifications download pdf (Page 65)

CHAPTER 3

Communication Channels

Communicating with an IBM PC 53

Unlike the serial port, the Centronics parallel input allows no parameters. It always

accepts 8-bit data with no parity, and it reserves the same set of characters for communi-

cation functions that the serial port reserves, with the exception of XON/XOFF

characters, which are passed through the PostScript interpreter, since ﬂow control is

maintained by means of the /BUSY signal.

The Centronics parallel interface is essentially an input-only channel. This means it

basically transfers information from the host to the printer. However, the PostScript

interpreter always deals with both the input and output sides of an I/O channel.

When operating in Centronics parallel input mode, the printer sets up the 8-pin serial

port for the PostScript language print operator. The output from this port may be ignored

for simple one-way communication. However, important information may be output via

this port. Printer errors are always reported, since the Paper Error signal on the

Centronics interface cannot be relied upon to report all printer errors. Table 3-6

summarizes the settings for the serial communications port when it is used as the output

port during parallel communication.

Serial Interface 3

You may also use the serial port as an alternative means of communicating with the

IBM PC, using either DTR or XON/XOFF ﬂow control. DTR ﬂow control is preferred,

since this is the default serial ﬂow control for the LaserWriter Select 310 printer.

DTR 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 DTR ﬂow control, issue the following MS-DOS commands to

your computer:

MODE COM1:19200,N,8,1,P

MODE LPT1:=COM1:

Table 3-6 Settings for the serial output channel during parallel communication

Parameter Settings

Data bits 8

Parity None

Stop bits 1

Flow control DTR

Baud rate 9600

Protocol Binary

1 2 ... 60 61 62 63 64 65 66 67 68

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Apple LaserWriter Select 310 Specifications Page 65