Image Processor; Image Rendering Technology - Tektronix Phaser 440 Service Manual

5
Theory of Operation

Image processor

Image rendering technology

5-16 Phaser 440 Color Printer
The image processor board handles PostScript data sent from a host computer
and transforms it into a format suitable for the print engine. The
hardware/software structure that performs this function is called a graphics
pipeline . The graphics pipeline is composed of five basic parts.
The I/O serializer handles the communication and protocol with the
host computers connected to the serial, parallel, Ethernet, and
LocalTalk ports as well as the SCSI port. A special portion of the I/O
serializer is dedicated to handling the multi-layered AppleTalk
protocol.
The PostScript data received through the I/O serializer is routed to the
PostScript interpreter . The PostScript interpreter generates display lists
which describe objects and text fonts as they are to appear on the
printed page. As needed, the PostScript interpreter reads font data
stored in ROMs on the image processor board. The PostScript
interpreter also handles errors it encounters in the PostScript data.
The PostScript interpreter's display list is, in turn, routed to the
rasterizer . The rasterizer converts the objects and fonts into a
bitmapped image composed of color planes. Color planes are bitmaps
of the primary colors cyan, magenta and yellow that make up the
image.
The engine driver outputs the color bitmaps to the print engine. It
handles the data transfer buffering and basic input/output functions.