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7/27/2019 ch9-3
1/40
2000 MorganKaufman Overheads forComputers asComponents
System design techniques
Private branch exchange (PBX).
Ink-jet printer.
PDAs.
Set-top boxes.
Systems-on-silicon.
7/27/2019 ch9-3
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2000 MorganKaufman Overheads forComputers asComponents
Digital telephone switches
High-end switches are highly reliable:
30 seconds downtime per year.
Companies, homes install private branchexchanges (PBXs):
intercom features;
management of long distance charges.
7/27/2019 ch9-3
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2000 MorganKaufman Overheads forComputers as
Components
Telephone switching
systems
Establish telephone calls:
within switch, find other phone line;
outside switch, find route to other line.
Route voice samples between phones.
Measure call time for billing.
Provide maintenance access to switch.
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Overheads forComputers as
Components
Telephone terminology
Line: distinct telephone connection.
Line card: PBX/subscriber line interface.
Off-hook: active telephone.
On-hook: inactive telephone.
Trunk line: phone lines between switches.
POTS: plain old telephone service (analog,no fancy services).
7/27/2019 ch9-3
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Overheads forComputers as
Components
Computer-controlled
telephone switching
Voice data rates:
8 bits sample (m or Alaw);
125 m s period (8kHz).
Telephones are I/O
devices.Computer bus is
switch.
CPU
memory
line
card
linecard
7/27/2019 ch9-3
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Dialing
Dual-tone multi-frequency (DTMF):tones define row,column of key.
Must be held for 0.1sec.
1 2 3
4 5 6
7 8 9
* 0 #
7/27/2019 ch9-3
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Overheads forComputers as
Components
Call states
On-hook
Rcv ringing
Call
Off-hookDial
toneDialing
Place
ringing
Receive call
Place call
Incoming
call
Take off-hook
Return on-hook
Take off-hook
Dial decoder ready
Number
complete
Other phone
off-hook
Line 1
Line 2
7/27/2019 ch9-3
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Components
PBX model
Calls are parallel processes:
Call coordination, billing, etc.
Call 1 Call n...
7/27/2019 ch9-3
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Overheads forComputers as
Components
Tigerswitch system
architecture
PC platform.
Switch calls over ISA bus.
Line cards are custom devices.
7/27/2019 ch9-3
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Overheads forComputers as
Components
DTMF sensing
Software process onCPU.
Uses lots of CPU time.
Analog filter bank online cards.
Expensive in volume.
DSP on separatecard.
Requires new design.
CPU
memory
line
card
line
card
DTMF card
7/27/2019 ch9-3
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Overheads forComputers as
Components
Switching
Process-per-call isbad implementation.
Context switch per callper 125 ms.
Unroll calls into oneloop.
Each loop iteration isone call for onesample.
for (i=0; i
7/27/2019 ch9-3
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Overheads forComputers as
Components
HP DesignJet drafting
plotter
Plots up to 36 inches wide at 300 DPI.
Combines a variety of tasks:
host communication;
graphics language interpretation;
rasterization;
device control.
7/27/2019 ch9-3
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Components
The plotting process
HP-GL/2 PostScript
rasterizer
raster memory
plottercontroller
7/27/2019 ch9-3
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Overheads forComputers as
Components
Design considerations
Memory utilization is important.
36 inches X large X 300 DPI X n bits/pixel is
a lot of memory.Requires clever algorithms to minimize raster
memory requirements.
Requires real-time control.Requires concurrency: read new data,
rasterize, control print head.
7/27/2019 ch9-3
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Overheads forComputers as
Components
HP DesignJet hardware
architecture
i960KAadrs
latch
busif
1 MB
ROM
2 MB
DRAM
proc.
support
ASIC
||
if
RS-
422
pen
ctrl
ASIC
swath
RAM
servo
proc.(8052)
EEPROM
DRAM
ctrlfront panel steppermotor
carriage
PC board
7/27/2019 ch9-3
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Components
Early architectural
decisions
Chose Intel 80960KA as main processor.
Handled parsing, rasterization control, print
engine control.Multiplexed bus reduced pin count.
Could be upgraded to floating-point ifnecessary.
Used modular I/O to host system.
Did not use disk for local storage.
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Components
System components
2 MB RAM (SIMM sockets for more).
Three ASICs:
pen interface;
processor support;
carriage.
Servo processing performed by 8052microcontroller.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Rasterization
Plot is generated in swaths.
Separate swath memory.
Pixels are generated in row order by mainprocessor.
Pixels are fed to pens in column order.
Pen interface ASIC transforms row orderto column order.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Data flows
i960KAadrs
latch
busif
1 MB
ROM
2 MBDRAM
proc.
support
ASIC
||
if
RS-
422
penctrl
ASIC
swath
RAM
servo
proc.
(8052)
EEPROM
DRAM
ctrlfront panel steppermotor
carriage
PC board
parsing and rasterization
swath generation
drawing
7/27/2019 ch9-3
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Overheads forComputers as
Components
Operations
Servo processor controls stepper motor.
Carriage processor must write, read pen
alignment marks.Processor support ASIC provides multiple
functions: interrupt and mailbox
communication.Motion controller decodes position of print
carriage and paper; watchdogs servo.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Pen interface ASIC
Interfaces to i960 bus, swath memory,carriage ASIC.
Pen interface reads pixels from swath inpredetermined pattern using pixel addressgenerator.
Must support bidirectional printing sincehead prints both ways.
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Components
Carriage ASIC
Interrfaces to processor bus, peninterface ASIC, servo controller.
Reads timing control registers using theCPU bus.
Delay registers add correction for pen
alignment.
7/27/2019 ch9-3
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Components
Development process
Pixel shuffling algorithm for peninterface/carriage ASICs was prototyped
in C.Built emulators for ASICs to allow parallel
development of i960 software and
hardware.
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Software development
environment
Plotter software could be run on Unixworkstation or target platform.
Differed in I/O and print engine subsystems.Print engine was emulated on host with X
window interface showing swath state.
Used in-house RTOS.HP-GL/2 parser was legacy code.
7/27/2019 ch9-3
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Components
Software development
environment, contd.
Rewrote vector/raster converter fromassembly language to C to port to i960.
Used gdb960 as monitor debugger ontarget system, communicating with host.
Front panel developed on PC, tested by
user interface designers, marketing.Paper loading designed by mechanical
engineers.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Personal digital assistant
PDA: portable, specialized informationdevice.
Characteristics:low cost for consumer market;
physically small;
battery-powered;software-rich.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Apple Newton
First modern PDA.
Original used ARM 610; later version used
StrongARM.Support operations in Runt ASIC: DMA,
real-time clock, video interface, audio,
PCMCIA.Software written in NewtonScript
language.
N t h d
7/27/2019 ch9-3
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Components
Newton hardware
architecture
ARM 610 ROM RAM
Runt
ASIC
LCD
speaker
serial I/F
A/D
tablet
PCMCIA
infrared
M t l E h d
7/27/2019 ch9-3
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Components
Motorola Envoy hardware
architecture
PCMCIA 1 MB DRAM 4 MB flash
Astro
system
ASIC
68439
CPU
audio
modem
infrared
power supply
A/Dtouchscreen
Magicbus
7/27/2019 ch9-3
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Overheads forComputers as
Components
Feature creep
Designers tend to add features to systemduring design.
Increases power consuption.Changes mechanical design.
Makes software design more complex.
Software thrashing can reduce batterylife.
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Components
PDA power supply
System must be designed to gracefullyhandle low battery power.
Abrupt power loss can destroy lots of data inRAM.
Smart Battery System puts electronics in
battery to measure battery performance.
7/27/2019 ch9-3
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Components
InfoPad
Brodersen et al: advanced networkedmultimedia information appliance.
System performed many functions onremote systems to increase battery life.
Made use of specialized hardware units to
reduce power consumption over softwareimplementation.
I f P d h d
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Components
InfoPad hardware
architecture
Wireless network
interface
Speechcodec
Video
decompressor
ARM 60
display
Keyboard/pointer
other I/O
7/27/2019 ch9-3
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Overheads forComputers as
Components
Set-top boxes
Interface between cable/satellite and TV:
digital television;
user interface;may include back channel for purchases, etc.
Very cost-sensitive market.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Set-top box in system
set-top box
IR
digital TV input
back
channel
Phili fib t b b
7/27/2019 ch9-3
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Components
Philips fiber-to-curb box
hardware
Network
interfaceMPEG
demux
MPEG
audio
MPEGvideo
NTSC
CD-I
graphicsPCMCIA
DRAM
I/Okbd
IR
card
NVRAM
DRAM
DRAM
7/27/2019 ch9-3
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Overheads forComputers as
Components
Fiber-to-curb box software
default apps custom apps
OS-9 kernel I/O manager
device driversboot/monito
rsoftware
MPEG2
demuxaudio/video
interfaces
CD-I
graphics
network
interface
processor
hardware
layer
OS
layer
application
layer
7/27/2019 ch9-3
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Overheads forComputers as
Components
Systems-on-silicon
Can build significant embedded systemson single chip:
one or more high-performance CPUs;I/O devices;
memory.
Advantages:higher performance and lower power;
lower cost.
7/27/2019 ch9-3
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Overheads forComputers as
Components
Moores Law (Sematech)
108
109
2000 2012
PC on chip
billion-transistor
system-on-chip
7/27/2019 ch9-3
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C t
Design challenges
Core-based design: cant take time todesign gates, lines of code.
Custom architectures:heterogeneous multiprocessors;
custom memory systems.
Verification:long turnaround time;
cant probe interior directly.