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HIGH-LEVEL VIEW OF PLOTTING PROCESS
HP-GL/2
HP Graphics Language. Postscript Page Description Language.
Page script is interpreted and then converted into raster
format.
Raster Format
Picture in two dimensional array of dots. Quadruplet of intensities Red, Green, Blue, Black.
Plotter Controller Reads rasterized image and sends
command to plotter carriage to put ink on paper.
Print engine
Plotter carriage and other units.
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HIGH-LEVEL VIEW OF PLOTTING PROCESS
HP-GL/2 PostScript
Rasterizer
Raster memory
Plotter controller
PLOTTERCARRIAGE
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DESIGN CONSIDERATIONS
Memory space is important
36 inch plot at 300 dpi.
Reduce the amount of raster memory.
Real time control is required
Very high speed control to transfer ink to paper.
Intensity must be controlled.
Head is scanned across page and paper moved with servo
Multiple events are happening at once
Events are ink jets, Head, Paper, Carriage.
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ARCHITECTURAL DIFFICULTIES
Specialized graphics processors too slow
General purpose processor
for parsing
Graphics chip raster conversion.
DESIGN COMPONENTS
Single RISC microprocessor
Intel 80960 KA
Modular I/O port
RS 232/422 and parallel interfaces
Single inline Memory Modules(SIMM)
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HARDWARE DESIGN
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CONT...
RISC microprocessor
Two microcontrollers
Three Application specific IC
Pen interface ASIC
Processor support ASIC
Carriage ASIC
Servo processor controls servo motor on print carriage,
front panel display, scans keyboard and runs service
station
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PARSING & RASTERIZATION
Page description comes through I/O port to mainprocessor and memory
Page description is parsed and pixels are generated.
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SWATH GENERATION
Generated pixels are stored in swath section of rasterized plot.
Swath memory is kept separated from main processor memory
Pixels from main processor are in row order which must be fed incolumn
Swath memory is used by pen interface ASIC.
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DRAWING
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PROCESSOR SUPPORT ASIC
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CONT...
It connects 960 and servo processor
Main processor allows it to talk to 960 and generateinterrupts.
Servo processor interface talks to 8052
Intercommunication block communication between two
processors. Motion controller decodes position of print carriage and
paper axes.
Fire pulse controller synchronizing output for each
column of pen data DRAM controller refresh signals
Serial I/O interface basic RS-232/422 interface.
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PEN INTERFACE ASIC
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CONT...
Key component of shuffler subsystem
Pixel address generator SRAM array for programmable
sequencer, column counter, adder.
Pixel counter
counts number of pixels to be printed
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CARRIAGE ASIC
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CONT..
Delayed pipeline registers are programmed with delay
values in order to control pen alignment.
Shuffling algorithm in pen interface and carriage ASIC
Algorithm were developed using Behavioural model in C
Graphical stubs for both input and output are used to
visualize the result
Processor-support and pen-notify ASIC were build with
combination of fast high speed PLD, standard parts, UART
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SOFTWARE DESIGN
Three challenges faced by designers
Hardware platform not available for several months
Unfamiliar with 960
Team was small
Software development environment run on Unix
workstation
Main processor was developed around Real Time
Operating System(RTOS)
HP-GL/2 language subsystem was used on printers.
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THANK YOU
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