Digital Camra Design

8/9/2019 Digital Camra Design

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Embedded Systems Design: A Unified

Hardware/Software Introduction

1

Chapter Digita! Camera E"amp!e


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Embedded Systems Design: A UnifiedHardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %

*ut!ine

Introduction to a simp!e digita! camera

Designer+s perspecti)e

,e-uirements specification

Design .our imp!ementations


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Embedded Systems Design: A UnifiedHardware/Software Introduction,#c$ %&&& 'ahid/(i)argis

0utting it a!! together (enera!purpose processor

Sing!epurpose processor Custom

Standard

2emory

Interfacing

3now!edge app!ied to designing a simp!e digita!

camera (enera!purpose )s4 sing!epurpose processors

0artitioning of functiona!ity among different processor types

Introduction


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Embedded Systems Design: A UnifiedHardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 5

Introduction to a simp!e digita! camera

Captures images

Stores images in digita! format 6o fi!m

2u!tip!e images stored in camera

6umber depends on amount of memory and bits used per image Down!oads images to 0C

*n!y recent!y possib!e Systemsonachip

2u!tip!e processors and memories on one IC

Highcapacity f!ash memory 'ery simp!e description used for e"amp!e

2any more features with rea! digita! camera 'ariab!e si7e images8 image de!etion8 digita! stretching8 7ooming in and out8 etc4


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Embedded Systems Design: A UnifiedHardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 9

Designer+s perspecti)e

wo ;ey tas;s 0rocessing images and storing in memory


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Embedded Systems Design: A UnifiedHardware/Software Introduction,#c$ %&&& 'ahid/(i)argis =

Chargecoup!ed de)ice #CCD$

Specia! sensor that captures an image

>ightsensiti)e si!icon so!idstate de)ice composed of many ce!!s

ens area

0i"e! co!umns

Co)ered co!umns

E!ectronic

circuitry

E!ectro

mechanica!

shutter

0i"e!rows


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis ?

Compression

Store more images

ransmit image to 0C in !ess time

0E( #oint 0hotographic E"perts (roup$ 0opu!ar standard format for representing digita! images in a compressed

form 0ro)ides for a number of different modes of operation

2ode used in this chapter pro)ides high compression ratios using DC#discrete cosine transform$

Image data di)ided into b!oc;s of ? " ? pi"e!s

steps performed on each b!oc; DC

uanti7ation

Huffman encoding


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis

DC step

ransforms origina! ? " ? b!oc; into a cosinefre-uencydomain Upper!eft corner )a!ues represent more of the essence of the image

>owerright corner )a!ues represent finer detai!s

Can reduce precision of these )a!ues and retain reasonab!e image -ua!ity

.DC #.orward DC$ formu!a C#h$ F if #h FF &$ then 1/s-rt#%$ e!se 14&

Au"i!iary function used in main function .#u8)$

.#u8)$ F G " C#u$ " C#)$ "F&44 yF&44 D"y " cos##%u J 1$u/1=$ " cos##%y J 1$)/1=$

(i)es encoded pi"e! at row u8 co!umn ) D"y is origina! pi"e! )a!ue at row "8 co!umn y

IDC #In)erse DC$ ,e)erses process to obtain origina! b!oc; #not needed for this design$


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 1&

uanti7ation step

Achie)e high compression ratio by reducing image-ua!ity ,educe bit precision of encoded data

.ewer bits needed for encoding

*ne way is to di)ide a!! )a!ues by a factor of % Simp!e right shifts can do this

De-uanti7ation wou!d re)erse process for decompression

1150 39 -43 -10 26 -83 11 41

-81 -3 115 -73 -6 -2 22 -5

14 -11 1 -42 26 -3 17 -38

2 -61 -13 -12 36 -23 -18 5

44 13 37 -4 10 -21 7 -8

36 -11 -9 -4 20 -28 -21 14

-19 -7 21 -6 3 3 12 -21

-5 -13 -11 -17 -4 -1 7 -4

144 5 -5 -1 3 -10 1 5

-10 0 14 -9 -1 0 3 -1

2 -1 0 -5 3 0 2 -5

0 -8 -2 -2 5 -3 -2 1

6 2 5 -1 1 -3 1 -1

5 -1 -1 -1 3 -4 -3 2

-2 -1 3 -1 0 0 2 -3

-1 -2 -1 -2 -1 0 1 -1

After being decoded using DC After -uanti7ation

Di)ide each ce!!+s

)a!ue by ?


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 11

Seria!i7e ? " ? b!oc; of pi"e!s 'a!ues are con)erted into sing!e !ist using 7ig7ag pattern

0erform Huffman encoding 2ore fre-uent!y occurring pi"e!s assigned short binary code

>onger binary codes !eft for !ess fre-uent!y occurring pi"e!s Each pi"e! in seria! !ist con)erted to Huffman encoded )a!ues

2uch shorter !ist8 thus compression

Huffman encoding step


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 1%

Huffman encoding e"amp!e

0i"e! fre-uencies on !eft 0i"e! )a!ue K1 occurs 19 times

0i"e! )a!ue 15 occurs 1 time

Bui!d Huffman tree from bottom up Create one !eaf node for each pi"e!

)a!ue and assign fre-uency as node+s)a!ue

Create an interna! node by @oining anytwo nodes whose sum is a minima!)a!ue

his sum is interna! nodes )a!ue

,epeat unti! comp!ete binary tree

ra)erse tree from root to !eaf toobtain binary code for !eaf+s pi"e!

)a!ue Append & for !eft tra)ersa!8 1 for right

tra)ersa!

Huffman encoding is re)ersib!e 6o code is a prefi" of another code

155

9 %

1 & %

1

1& 9

5 ? =151 1

%

1 1

%

1

%%

5

9

5

=9

9

1

&

9

1

19

1

5

=

1

?

1

?19

%

9

=

5

1

-1 15x

0 8x

-2 6x1 5x

2 5x

3 5x

5 5x

-3 4x

-5 3x

-10 2x

144 1x

-9 1x

-8 1x

-4 1x

6 1x

14 1x

-1 00

0 100

-2 110

1 010

2 1110

3 1010

5 0110

-3 11110

-5 10110

-10 01110

144 111111

-9 111110

-8 101111

-4 101110

6 011111

14 011110

0i"e!

fre-uenciesHuffman tree

Huffman

codes


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Archi)e step

,ecord starting address and image si7e Can use !in;ed !ist

*ne possib!e way to archi)e images If ma" number of images archi)ed is 6:

Set aside memory for 6 addresses and 6 imagesi7e )ariab!es 3eep a counter for !ocation of ne"t a)ai!ab!e address

Initia!i7e addresses and imagesi7e )ariab!es to &

Set g!oba! memory address to 6 " 5 Assuming addresses8 imagesi7e )ariab!es occupy 6 " 5 bytes

.irst image archi)ed starting at address 6 " 5

(!oba! memory address updated to 6 " 5 J #compressed image si7e$

2emory re-uirement based on 68 image si7e8 and a)eragecompression ratio


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Up!oading to 0C


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,e-uirements Specification

System+s re-uirements K what system shou!d do 6onfunctiona! re-uirements

Constraints on design metrics #e4g48 Lshou!d use &4&&1 watt or !essM$

.unctiona! re-uirements

System+s beha)ior #e4g48 Loutput N shou!d be input O times %M$ Initia! specification may be )ery genera! and come from mar;eting dept4

E4g48 short document detai!ing mar;et need for a !owend digita! camera that:

captures and stores at !east 9& !owres images and up!oads to 0C8

costs around P1&& with sing!e mediumsi7e IC costing !ess that P%98

has !ong as possib!e battery !ife8

has e"pected sa!es )o!ume of %&&8&&& if mar;et entry Q = months8

1&&8&&& if between = and 1% months8

insignificant sa!es beyond 1% months


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 1=

6onfunctiona! re-uirements

Design metrics of importance based on initia! specification Performance: time re-uired to process image

Size: number of e!ementary !ogic gates #%input 6A6D gate$ in IC

Power: measure of a)g4 e!ectrica! energy consumed whi!e processing

Energy: battery !ifetime #power " time$

Constrained metrics 'a!ues mustbe be!ow #sometimes abo)e$ certain thresho!d

*ptimi7ation metrics

Impro)ed as much as possib!e to impro)e product 2etric can be both constrained and optimi7ation


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6onfunctiona! re-uirements #cont4$

0erformance 2ust process image fast enough to be usefu!

1 sec reasonab!e constraint S!ower wou!d be annoying

.aster not necessary for !owend of mar;et

herefore8 constrained metric

Si7e 2ust use IC that fits in reasonab!y si7ed camera

Constrained and optimi7ation metric Constraint may be %&&8&&& gates8 but sma!!er wou!d be cheaper

0ower 2ust operate be!ow certain temperature #coo!ing fan not possib!e$

herefore8 constrained metric

Energy ,educing power or time reduces energy

*ptimi7ed metric: want battery to !ast as !ong as possib!e


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 1?

Informa! functiona! specification

.!owchart brea;s functiona!ity

down into simp!er functions

Each function+s detai!s cou!d then

be described in Eng!ish

Done ear!ier in chapter

>ow -ua!ity image has reso!ution

of =5 " =5

2apping functions to a particu!ar

processor type not done at this

stage

seria! output

e4g48 &11&1&444

yes no

CCD

input

erobias ad@ust

DC

uanti7e

Archi)e in

memory

2ore

?R?

b!oc;s

ransmit seria!!y

yes

no Done


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,efined functiona! specification

,efine informa! specification intoone that can actua!!y be e"ecuted

Can use C/CJJ code to describeeach function Ca!!ed system!e)e! mode!8

prototype8 or simp!y mode! A!so is first imp!ementation

Can pro)ide insight into operationsof system 0rofi!ing can find computationa!!y

intensi)e functions

Can obtain samp!e output used to)erify correctness of fina!imp!ementation

image fi!e

1&1&11&1&

11&1&1&1&

&1&1&11&14

44

CCD4C

C6,>4C

UA,4C

output fi!e

1&1&1&1&1

&1&1&1&1&

1&1&1&1&1

&444

C*DEC4CCCD004C

E"ecutab!e mode! of digita! camera


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %&

CCD modu!e

Simu!ates rea! CCD

CcdInitializeis passed name of image fi!e

CcdCaturereads LimageM from fi!e

Ccd!o!i"eloutputs pi"e!s one at a time

char CcdPopPixel(void) {

char pixel;

pixel = buffer[rowIndex][colIndex];

if( ++colIndex == SZC!" ) {

colIndex = #; if( ++rowIndex == SZ$!% ) {

colIndex = &';

rowIndex = &';

reurn pixel;

*include ,dio-h.

*define SZ$!% /0

*define SZC!" (/0 + 1)

,aic 2I"3 4i5a6e2ile7andle;

,aic char buffer[SZ$!%][SZC!"];

,aic un,i6ned rowIndex8 colIndex;

void CcdIniiali9e(con, char 4i5a6e2ile:a5e) {

i5a6e2ile7andle = fopen(i5a6e2ile:a5e8 r);

rowIndex = &';

colIndex = &';

void CcdCapure(void) { in pixel;

rewind(i5a6e2ile7andle);

for(rowIndex=#; rowIndexSZ$!%; rowIndex++) {

for(colIndex=#; colIndexSZC!"; colIndex++) {

if( f,canf(i5a6e2ile7andle8


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %1

CCD00 #CCD 0re0rocessing$ modu!e

0erforms 7erobias ad@ustment CcdCatureuses CcdCatureand Ccd!o!i"elto obtain

image

0erforms 7erobias ad@ustment after each row read in

*define SZ$!% /0

*define SZC!" /0

,aic char buffer[SZ$!%][SZC!"];

,aic un,i6ned rowIndex8 colIndex;

void CcdppIniiali9e() {

rowIndex = &';

colIndex = &';

void CcdppCapure(void) {

char bia,;

CcdCapure(); for(rowIndex=#; rowIndexSZ$!%; rowIndex++) {


buffer[rowIndex][colIndex] = CcdPopPixel();

bia, = (CcdPopPixel() + CcdPopPixel()) > 1;


buffer[rowIndex][colIndex] &= bia,;

rowIndex = #;

colIndex = #;

char CcdppPopPixel(void) {

char pixel;

pixel = buffer[rowIndex][colIndex];

if( ++colIndex == SZC!" ) {

colIndex = #;

if( ++rowIndex == SZ$!% ) {

colIndex = &';

rowIndex = &';

reurn pixel;


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %%

UA, modu!e

Actua!!y a ha!f UA, *n!y transmits8 does not recei)e

UartInitializeis passed name of fi!e to output to

UartSendtransmits #writes to output fi!e$ bytes at a time

*include ,dio-h.

,aic 2I"3 4oupu2ile7andle;

void ?arIniiali9e(con, char 4oupu2ile:a5e) {

oupu2ile7andle = fopen(oupu2ile:a5e8 w);

void ?arSend(char d) {

fprinf(oupu2ile7andle8


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %

C*DEC modu!e

2ode!s .DC encoding

ibufferho!ds origina! ? " ? b!oc;

obufferho!ds encoded ? " ? b!oc;

Codec!us#!i"el ca!!ed =5 times to fi!!

ibuffer with origina! b!oc;

CodecDo$dctca!!ed once to

transform ? " ? b!oc;

E"p!ained in ne"t s!ide

Codec!o!i"el ca!!ed =5 times to

retrie)e encoded b!oc; from obuffer

,aic ,hor ibuffer[A][A]8 obuffer[A][A]8 idx;

void CodecIniiali9e(void) { idx = #;

void CodecBo2dc(void) {

in x8 ;

for(x=#; xA; x++) {

for(=#; A; ++)

obuffer[x][] = 2BCD(x8 8 ibuffer);

idx = #;

void CodecPu,hPixel(,hor p) {

if( idx == /0 ) idx = #;

ibuffer[idx > A][idx < A] = p; idx++;

,hor CodecPopPixel(void) {

,hor p;

if( idx == /0 ) idx = #;

p = obuffer[idx > A][idx < A]; idx++;

reurn p;


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C*DEC #cont4$

Imp!ementing .DC formu!a C#h$ F if #h FF &$ then 1/s-rt#%$ e!se 14&

.#u8)$ F G " C#u$ " C#)$ "F&44 yF&44 D"y "

cos##%u J 1$u/1=$ " cos##%y J 1$)/1=$

*n!y =5 possib!e inputs to C%S8 so tab!e canbe used to sa)e performance time

.!oatingpoint )a!ues mu!tip!ied by %8=? androunded to nearest integer

%8=? chosen in order to store each )a!ue in %

bytes of memory

.i"edpoint representation e"p!ained more !ater

$DC& unro!!s inner !oop of summation8imp!ements outer summation as twoconsecuti)e for !oops

,aic con, ,hor C!SDEF"3[A][A] = {

{ G1H/A8 G1'GA8 G#1HG8 1H108 1G'H#8 'A1#08 '1GJ8 /GJ1 8

{ G1H/A8 1H108 '1GJ8 &/GJ18 &1G'H#8 &G1'GA8 &G#1HG8 &'A1#0 8

{ G1H/A8 'A1#08 &'1GJ8 &G1'GA8 &1G'H#8 /GJ18 G#1HG8 1H10 8

{ G1H/A8 /GJ18 &G#1HG8 &'A1#08 1G'H#8 1H108 &'1GJ8 &G1'GA 8

{ G1H/A8 &/GJ18 &G#1HG8 'A1#08 1G'H#8 &1H108 &'1GJ8 G1'GA 8

{ G1H/A8 &'A1#08 &'1GJ8 G1'GA8 &1G'H#8 &/GJ18 G#1HG8 &1H10 8

{ G1H/A8 &1H108 '1GJ8 /GJ18 &1G'H#8 G1'GA8 &G#1HG8 'A1#0 8

{ G1H/A8 &G1'GA8 G#1HG8 &1H108 1G'H#8 &'A1#08 '1GJ8 &/GJ1

;

,aic in 2BCD(in u8 in v8 ,hor i56[A][A]) {

double ,[A]8 r = #; in x;

for(x=#; xA; x++) {

,[x] = i56[x][#] 4 C!S(#8 v) + i56[x]['] 4 C!S('8 v) +

i56[x][1] 4 C!S(18 v) + i56[x][G] 4 C!S(G8 v) +

i56[x][0] 4 C!S(08 v) + i56[x][] 4 C!S(8 v) +

i56[x][/] 4 C!S(/8 v) + i56[x][H] 4 C!S(H8 v);

for(x=#; xA; x++) r += ,[x] 4 C!S(x8 u);

reurn (,hor)(r 4 -1 4 C(u) 4 C(v));

,aic ,hor !:3!K3$SL$DD%! = 1G'H#;

,aic double C!S(in x8 in uv) {

reurn C!SDEF"3[x][uv] > G1H/A-#;

,aic double C(in h) {

reurn h M '-# N !:3!K3$SL$DD%! > G1H/A-#;


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C6,> #contro!!er$ modu!e

Heart of the system CntrlInitializefor consistency with other modu!es on!y

CntrlCatureImageuses CCD00 modu!eto input

image and p!ace in buffer

CntrlComressImagebrea;s the =5 " =5 buffer into ? "

? b!oc;s and performs .DC on each b!oc; using the

C*DEC modu!e

A!so performs -uanti7ation on each b!oc;

CntrlSendImagetransmits encoded image seria!!y usingUA, modu!e

void CnrlSendI5a6e(void) { for(i=#; iSZ$!%; i++)

for(O=#; OSZC!"; O++) {

e5p = buffer[i][O]; ?arSend(((char4)e5p)[#]); >4 ,end upper be 4>

?arSend(((char4)e5p)[']); >4 ,end lower be 4>

*define SZ$!% /0

*define SZC!" /0

*define :?$!%F"!CQS (SZ$!% > A)

*define :?C!"F"!CQS (SZC!" > A)

,aic ,hor buffer[SZ$!%][SZC!"]8 i8 O8 R8 l8 e5p;

void CnrlIniiali9e(void) {

void CnrlCapureI5a6e(void) {

CcdppCapure();

for(i=#; iSZ$!%; i++)

for(O=#; OSZC!"; O++)

buffer[i][O] = CcdppPopPixel();

void CnrlCo5pre,,I5a6e(void) {

for(i=#; i:?$!%F"!CQS; i++) for(O=#; O:?C!"F"!CQS; O++) {

for(R=#; RA; R++)

for(l=#; lA; l++)

CodecPu,hPixel(

(char)buffer[i 4 A + R][O 4 A + l]);

CodecBo2dc();>4 par ' & 2BCD 4>

for(R=#; RA; R++)

for(l=#; lA; l++) {

buffer[i 4 A + R][O 4 A + l] = CodecPopPixel();

>4 par 1 & uani9aion 4>

buffer[i4A+R][O4A+l] ..= /;


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %=

0utting it a!! together

'ain initia!i7es a!! modu!es8 then uses C6,> modu!e to capture8

compress8 and transmit one image

his system!e)e! mode! can be used for e"tensi)e e"perimentation

Bugs much easier to correct here rather than in !ater mode!s

in 5ain(in ar6c8 char 4ar6v[]) {

char 4uar!upu2ile:a5e = ar6c . ' M ar6v['] N uarou-x; char 4i5a6e2ile:a5e = ar6c . 1 M ar6v[1] N i5a6e-x;

>4 iniiali9e he 5odule, 4>

?arIniiali9e(uar!upu2ile:a5e); CcdIniiali9e(i5a6e2ile:a5e);

CcdppIniiali9e();

CodecIniiali9e();

CnrlIniiali9e(); >4 ,i5ulae funcionali 4>

CnrlCapureI5a6e(); CnrlCo5pre,,I5a6e();

CnrlSendI5a6e();


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Design

Determine system+s architecture 0rocessors

Any combination of sing!epurpose #custom or standard$ or genera!purpose processors

2emories8 buses

2ap functiona!ity to that architecture 2u!tip!e functions on one processor

*ne function on one or more processors Imp!ementation

A particu!ar architecture and mapping

So!ution space is set of a!! imp!ementations

Starting point >owend genera!purpose processor connected to f!ash memory

A!! functiona!ity mapped to software running on processor Usua!!y satisfies power8 si7e8 and timetomar;et constraints

If timing constraint not satisfied then !ater imp!ementations cou!d:

use sing!epurpose processors for timecritica! functions

rewrite functiona! specification


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis %?

Imp!ementation 1: 2icrocontro!!er a!one

>owend processor cou!d be Inte! ?&91 microcontro!!er ota! IC cost inc!uding 6,E about P9


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Imp!ementation %:

2icrocontro!!er and CCD00

CCD00 function imp!emented on custom sing!epurpose processor

Impro)es performance K !ess microcontro!!er cyc!es

Increases 6,E cost and timetomar;et

Easy to imp!ement

Simp!e datapath

.ew states in contro!!er

Simp!e UA, easy to imp!ement as sing!epurpose processor a!so

EE0,*2 for program memory and ,A2 for data memory added as we!!

?&91

UA, CCD00

,A2EE0,*2

SOC


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UA,

UA, in id!e mode unti! in)o;ed UA, in)o;ed when ?&91 e"ecutes store instruction

with UA,+s enab!e register as target address

2emorymapped communication between ?&91 and

a!! sing!epurpose processors

>ower ?bits of memory address for ,A2 Upper ?bits of memory address for memorymapped

I/* de)ices

Start state transmits & indicating start of byte

transmission then transitions to Data state

Data state sends ? bits seria!!y then transitions to

Stop state

Stop state transmits 1 indicating transmission done

then transitions bac; to id!e mode

in)o;ed

I F ?

I Q ?

Idle

:I F &

Start:ransmi

t >* descriptions and

functiona!!y simu!ates e"ecution of system ,eca!! program code trans!ated to 'HD>

description of ,*2

ests for correct functiona!ity

2easures c!oc; cyc!es to process oneimage #performance$

(ate!e)e! description obtained through

synthesis

Synthesis too! !i;e compi!er for S00s

Simu!ate gate!e)e! mode!s to obtain data

for power ana!ysis 6umber of times gates switch from 1 to &

or & to 1

Count number of gates for chip area

0ower

'HD>

simu!ator

'HD> 'HD> 'HD>

E"ecution time

Synthesis

too!

gates gates gates

Sum gates

(ate !e)e!

simu!ator

0ower

e-uation

Chip area

Obtaining design metrics of interest


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis =

Imp!ementation %:

2icrocontro!!er and CCD00

Ana!ysis of imp!ementation % ota! e"ecution time for processing one image:

41 seconds

0ower consumption: &4& watt

Energy consumption: &4& @ou!e #41 s " &4& watt$

ota! chip area: ?8&&& gates


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Imp!ementation : 2icrocontro!!er and

CCD00/.i"ed0oint DC

41 seconds sti!! doesn+t meet performance constraint

of 1 second

DC operation prime candidate for impro)ement

E"ecution of imp!ementation % shows microprocessorspends most cyc!es here

Cou!d design custom hardware !i;e we did for CCD00 2ore comp!e" so more design effort

Instead8 wi!! speed up DC functiona!ity by modifyingbeha)ior


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis ?

DC f!oatingpoint cost

.!oatingpoint cost DC uses T%=& f!oatingpoint operations per pi"e! transformation

5&= #=5 " =5$ pi"e!s per image

1 mi!!ion f!oatingpoint operations per image

6o f!oatingpoint support with Inte! ?&91 Compi!er must emu!ate

(enerates procedures for each f!oatingpoint operation

mu!t8 add

Each procedure uses tens of integer operations

hus8 W 1& mi!!ion integer operations per image

0rocedures increase code si7e

.i"edpoint arithmetic can impro)e on this


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.i"edpoint arithmetic

Integer used to represent a rea! number Constant number of integer+s bits represents fractiona! portion of rea! number

2ore bits8 more accurate the representation

,emaining bits represent portion of rea! number before decima! point

rans!ating a rea! constant to a fi"edpoint representation

2u!tip!y rea! )a!ue by % X #Y of bits used for fractiona! part$

,ound to nearest integer

E4g48 represent 415 as ?bit integer with 5 bits for fraction

%X5 F 1=

415 " 1= F 9&4%5 Z 9& F &&11&&1&

1= #%X5$ possib!e )a!ues for fraction8 each represents &4&=%9 #1/1=$ >ast 5 bits #&&1&$ F %

% " &4&=%9 F &41%9

#&&11$ J &41%9 F 41%9 Z 415 #more bits for fraction wou!d increase accuracy$


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 5&

.i"edpoint arithmetic operations

Addition Simp!y add integer representations

E4g48 415 J %41 F 94?9

415 [ 9& F &&11&&1&

%41 [ 5 F &&1&1&11

9& J 5 F F &1&111&1

9#&1&1$ J 1#11&1$ " &4&=%9 F 94?1%9 Z 94?9

2u!tip!y 2u!tip!y integer representations

Shift resu!t right by Y of bits in fractiona! part

E4g48 415 \ %41 F ?49&5

9& \ 5 F %19& F 1&&&&11&&11&

WW 5 F 1&&&&11&

?#1&&&$ J =#&11&$ " &4&=%9 F ?49 Z ?49&5

,ange of rea! )a!ues used !imited by bit widths of possib!e resu!ting )a!ues


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I ! i 2i !! d


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Hardware/Software Introduction,#c$ %&&& 'ahid/(i)argis 5%

Imp!ementation : 2icrocontro!!er and

CCD00/.i"ed0oint DC

Ana!ysis of imp!ementation Use same ana!ysis techni-ues as imp!ementation %

ota! e"ecution time for processing one image: 149 seconds

0ower consumption: &4& watt #same as %$

Energy consumption: &4&9& @ou!e #149 s " &4& watt$

Battery !ife =" !onger^^

ota! chip area: &8&&& gates

?8&&& !ess gates #!ess memory needed for code$

I ! i 5


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Imp!ementation 5:

2icrocontro!!er and CCD00/DC

0erformance c!ose but not good enough

2ust resort to imp!ementing C*DEC in hardware

Sing!epurpose processor to perform DC on ? " ? b!oc;

?&91

UA, CCD0

0

,A2EE0,*2

SOCC*DEC


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C*DEC design

5 memory mapped registers C*DA&AI*)E/C*DA&A%*)Eused to

push/pop ? " ? b!oc; into and out ofC*DEC

C*C'-D*)Eused to commandC*DEC

4 bu, wai 4>

"ewritten CODEC software

I ! t ti 5


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Imp!ementation 5:

2icrocontro!!er and CCD00/DC

Ana!ysis of imp!ementation 5 ota! e"ecution time for processing one image:

&4& seconds #we!! under 1 sec$

0ower consumption:

&4&5& watt Increase o)er % and because S*C has another processor

Energy consumption: &4&&&5& @ou!e #&4& s " &4&5& watt$

Battery !ife 1%" !onger than pre)ious imp!ementation^^

ota! chip area: 1%?8&&& gates

Significant increase o)er pre)ious imp!ementations


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Digital Camra Design