System Data Flow; Display List - HP 200 Service Manual

System Data Flow

Data characters
One at a time
I/O Buffer
Data characters
500 Bytes
I/O Interrupt
Physical
Input/Output
Data
Input/Output
The user's computer is connected to the plotter through a physical input/output (I/O)
connection. The I/O interrupt process removes data from the I/O port, 500 bytes at a time,
and places it into the I/O buffer.
Parser
The parser removes data from the I/O buffer, one byte at a time, interprets the data and
transforms it into graphic objects, which are mapped onto the display list. The parser can
interpret either raster or vector data. It adds positional information to the data indicating
where it is placed on the display list. It continues building the display list until the entire
plot has been sent or until memory is full.

Display List

The graphic objects are geometrical shapes (arcs, vectors, etc.), which are placed on the
display list. The display list is a logical map. It is built in a swath format. The information
that builds the display list is stored in DRAM (Dynamic Random Access Memory). The more
DRAM the system contains, the larger and more dense the display list can be.
C3187 90000
Firmware Graphics
Module
Parser
Graphic
objects
Display List
Graphic
objects
VRC, RRC
Rasterized
object
Swath
Swath Holding Area
Physical
Swath Area
Swath
Firmware
Print-Engine
Control Module
Swath
Manager
Functional Overview 5 19