HP 220 - Manual (Page 51)

5Ć19 Functional Overview C3187Ć90000
System Data Flow
Firmware
Print-Engine
Control Module
Physical
Input/Output
Data
I/O Interrupt
I/O Buffer Parser
Display List
VRC, RRC
Swath Holding Area
Swath
Manager
Physical
Swath Area Data characters
500 Bytes
Data characters
One at a time
Graphic
objects
Graphic
objects
Swath
Swath
Rasterized
object
Firmware Graphics
Module
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 RandomĆAccess Memory). The more
DRAM the system contains, the larger and more dense the display list can be.