Apple LaserWriter Pro 630 Envelope Feeder Specifications download pdf (Page 37)

CHAPTER 2

LaserJet IIP Emulation

LaserJet IIP Emulation 2

The LaserWriter Pro printer has a built-in Hewlett Packard LaserJet IIP emulator, which

is compatible with Hewlett-Packard PCL (Printer Control Language), Level 4. Chapter 3

of this developer note, “LaserWriter Pro Software,” describes the features of the

emulator. Chapter 3 of the

LaserWriter Reference

provides more information on the subject.

Selecting Emulation 2

You may invoke the emulation in one of three ways. Each method is described brieﬂy

below. Before beginning the emulation, the

emulate

procedure erases the current page

and initializes the graphics state. It also clears the operand stack and the dictionary stack.

Running an emulator consumes some PostScript virtual memory. If

emulate

returns

normally with no interrupt that virtual memory is reclaimed. If

emulate

is invoked

when there is too little virtual memory, a virtual memory error,

VMerror,

occurs

You

should not call the

emulate

procedure when the printer is in interactive mode.

Setting the Server to Emulation Mode 2

You may set the server to an emulation mode, as described in the

LaserWriter Reference.

This method has the advantage of making the communication protocol the same as that

of the printer being emulated. However, it has the disadvantage that the channel must be

closed and reopened when you switch modes using the mode switch. When the channel

is closed, all buffered data is ﬂushed out, and any data sent from the host before the

channel is reopened is lost. This method is not appropriate if the host computer

frequently switches between sending PostScript language programs and receiving

emulation input.

Selecting From Within a PostScript Language Program 2

You may invoke the emulation from within a PostScript language program. This method

means the host computer can switch back and forth between PostScript language

programs and emulation inputs, and both types of data can be in the printer’s input

buffer at the same time without data loss.

A PostScript language program can invoke the emulator using a statusdict

procedure called emulate. This procedure takes a ﬁle and an emulator name from the

operand stack. The ﬁle is the input source for the emulation. The emulator name

operand selects the emulation to be invoked. To select the Hewlett-Packard LaserJet IIP

emulator, you must use the name /LaserJet IIP. To maintain compatibility with

older printers, the name /hpcl will also select the LaserJet IIP emulator. The following

example shows how to select the LaserJet emulator.

currentfile /LaserJetIIP statusdict /emulate get exec

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 96 97

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Apple LaserWriter Pro 630 Envelope Feeder Specifications Page 37

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