Apple LaserWriter Select 310 Specifications download pdf (Page 58)

CHAPTER 3

Communication Channels

46 Serial Communication

The LaserWriter Select 310 printer has two communication ports that support

two communication channels. One port is the RS-232 serial port used for serial

communication. The other is the Centronics parallel port used to connect the LaserWriter

Select 310 printer to an IBM-PC compatible computer. The section “Communication

Ports,” in Chapter 1, describes the physical characteristics of the connectors. This chapter

deals with the software support for the serial and parallel communication channels.

Serial Communication 3

When the LaserWriter Select 310 printer is in serial mode, it uses the RS-232 port to send

data and receive data encoded in ASCII. Certain characters serve special purposes. For

example, Control-D marks the end of the ﬁle, and Return indicates end of line. The server

performs a job by reading and executing a PostScript program from the serial port. When

it reads the end-of-ﬁle character and the program terminates, the server sends an

end-of-ﬁle character, ends the job, and starts a new one.

Three parameters control the details of serial communication. They are channel, baud

rate, and options. These parameters may be changed by invoking the statusdict

operator setsccbatch. Serial communication is asynchronous, start-stop, and uses

7 or 8 bits per character. The 8-pin serial connector is designated as a channel in the

PostScript interpreter by the integer 9. Table 3-1 summarizes the default settings for the

LaserWriter Select 310 printer serial communication channel.

Baud Rates 3

The baud rate is given as an integer, such as 1200 or 9600. The baud-rate parameter

may be any positive integer less than 100000. However, the hardware can only achieve

certain baud rates, and other values are rounded to the nearest achievable rate. Below

57600 baud, the achievable rates are 9600, 10473, 11520, 12800, 14400, 16457, 19200, 23040,

28800, and 38400. Any baud rate that divides into 115200 with a quotient of two or more

is legal. The Macintosh host computer supports a 57600 baud rate. Host systems other

than the Macintosh are most likely to support a 19200 baud rate.

Table 3-1 Default settings for the serial communication channel parameters

Parameter Default settings Other settings

Data bits 8 7

Parity None None

Stop bits One –

Flow control DTR XON/XOFF

Baud rate 57600 Any baud rate that divides into 115200 with a

quotient of two or more

Protocol Binary Simple

1 2 ... 53 54 55 56 57 58 59 60 61 62 63 ... 67 68

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Apple LaserWriter Select 310 Specifications Page 58