Apple LaserWriter Select 310 Printer - Manual (Page 22)

C H A P T E R 1
LaserWriter Select 310 Hardware
10 Basic Operation
DRAM Expansion 1
The LaserWriter Select 310 printer comes with 1.5 MB of DRAM installed on the printer’s
main circuit board. As shown in Figure 1-6, there are three DRAM devices: two 512K x 8
bit devices, and one 256K x 16 bit device. These three DRAMs present a 16-bit interface to
the microprocessor installed on the printed circuit board.
You can expand DRAM capability by adding a 72-pin SIMM (single in-line memory
module), which plugs into the SIMM connector on the circuit board. The LaserWriter
Select 310 printer supports SIMM cards with capacities of 1 MB and 4 MB. You must use a
32-bit wide SIMM card in this configuration.
Basic Operation 1
This section provides an overview of the LaserWriter Select 310 printer’s operating
modes. Since much of the printer’s behavior may be changed by changing the parameter
settings, as described in Chapter 2, this section assumes that all options that may be
adjusted are set to their standard values.
The main function of the LaserWriter Select 310 printer is to execute the PostScript
language programs sent to it from a computer. During normal operation, the printer
cycles endlessly through the following sequence of steps:
1. It sets up a clean initial execution environment (virtual memory) for the PostScript
language program. In effect, it is setting up a job.
2. It executes the job by interpreting the standard input files, which are received on either
the serial port or on the Centronics parallel port.
3. When the printer encounters an end-of-file character or when an error occurs, it cleans
up after the job and restores the virtual memory to its initial state in preparation for
the next job.
The main object of this process is to produce printed pages. However, a program may
change some permanent parameters in the printer itself, or it may perform some
computation that causes results to be sent back to the host computer, rather than causing
hard copy to be printed.
There are two basic modes of operation: batch and interactive.
Batch Mode 1
Batch mode is the normal way of operating the LaserWriter Select 310 printer . In this
mode it operates as a printing device for a computer.
A batch-mode job consists of executing a single file containing a PostScript language
program. When an end-of-file character is reached, or the PostScript language terminates,
the job is finished. In this mode, the only data transmitted from the LaserWriter Select 310
printer to the host is generated by the PostScript language printer operator or by errors.
The printer provides no echoing, editing, or other user amenities.