Es Lec7 Amba

7/23/2019 Es Lec7 Amba

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Lecture 7. AMBA

Prof. Taeweon SuhComputer Science Education

Korea University

COMP427 Embedded Systems



Korea Univ

AMBA

• Advanced Microcontroller us Architecture !n"chip #us protocol from A$M

• !n"chip interconnect speci%cation for the connectionand mana&ement of functional #loc's includin&processor and peripheral devices

(ntroduced in )**+

AMA is a re&istered trademar' of A$M,imited.

AMA is an open standard

2-i'ipedia



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AMBA istory

• AMBA AS AP

• AMBA 2 )***/ A0

• widely used on A$M12 A$M* and A$M Corte3"M #aseddesi&ns

AS AP4 or AP/

3-i'ipedia

• AMBA ! 4556/

A7(6 or A7( v).5/• widely used on A$M Corte3"A

processors includin& Corte3"A*

A0",ite v).5 AP6 v).5 AT v).5

• AMBA 4 45)5/ ACE

• widely used on the latest A$MCorte3"A processors includin&Corte3"A1 and Corte3"A)8

ACE",ite

A7(9 A7(9",ite A7("Stream v).5 AT v).) AP9 v4.5

ACE: A7( Coherency E3tensions

A7(: Advanced e7tensi#le (nterfaceA0: Advanced 0i&h"performance us

AS: Advanced System us

AP: Advanced Peripheral us

AT: Advanced Trace us



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ASB

4AMA Speci%cation ;4.5



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ASB

5

ard"are#evice $

ard"are#evice %

ard"are#evice 2

ard"are#evice !

ard"are#evice 4

ard"are#evice &

ASB



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AB



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AB "it' ! Masters and 4S(aves


<0= indicates A0 si&nals



AB Basic )rans*er E+am,(e "it'-ait


0$EA>? Source: Slave

-rite data

$ead data



AB Burst )rans*er E+am,(e


0$EA>? Source: Slave



A# S,(it )ransaction


• (f slave decides thatit may ta'e a num#erof cycles to o#tainand provide data2 it&ives a SP,(T transfer

response

• Ar#iter &rants use ofthe #us to othermasters

0$ESP: Transfer response fro slave !KA?2 E$$!$2 $ET$?2 and SP,(T/



APB -rite/ead




A01 v%.$

• AMA A7( protocol is tar&eted at hi&h"performance2 hi&h"fre@uency system desi&ns

• A7( 'ey features

Separate addresscontrol and data phases Support for unali&ned data transfers usin& #yte stro#es

Separate read and write data channels to ena#le low"cost >irect Memory Access >MA/

A#ility to issue multiple outstandin& addresses

!ut"of"order transaction completion

Easy addition of re&ister sta&es to provide timin&closure

12AMA A7( Speci%cation ;).5



& 1nde,endent C'anne(s

• /ead address c'anne( and -rite address c'anne( ;aria#le len&th #urst: ) B )+ data transfers

urst with a transfer sie of D B )549 #its ) B )4D/

• /ead data c'anne(

Convey data and any read response info. >ata #us can #e D2 )+2 642 +92 )4D2 48+2 8)42 or )549 #its

• -rite data c'anne(

>ata #us can #e D2 )+2 642 +92 )4D2 48+2 8)42 or )549 #its

• -rite res,onse c'anne( -rite response info.

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A01 /ead O,eration


/eadAddressC'anne(

/ead#ataC'anne(

$$EA>?: rom master2 indicate that master can accept the read data and response info.



A01 -rite O,eration


-riteAddressC'anne(-rite#ataC'anne(

-rite/es,onseC'anne(

-;A,(> Source: Master

-$EA>? Source: Slave

;A,(> Source: Slave

$EA>? Source: Master



Outo*order Com,(etion

• A7( &ives an (> ta& to every transaction Transactions with the same (> are completed in order

Transactions with diFerent (>s can #e completed out oforder




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1# Si3na(s


-riteAddressC'anne(

-rite#ataC'anne(

-rite/es,onseC'anne(

/eadAddress

C'anne(

/ead#ataC'anne(



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Outo*order Com,(etion

• !ut"of"order transactions can improve system

performance in 4 ways ast"respondin& slaves respond in advance of earlier

transactions with slower slaves

Comple3 slaves can return data out of order• A data item for a later access mi&ht #e availa#le #efore the data

for an earlier access is availa#le

• (f a master re@uires that transactions are completedin the same order that they are issued2 they must allhave the same (> ta&

• (t is not a re@uired feature Simple masters and slaves can process one transaction at

a time in the order they are issued




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Addition o* /e3ister S(ices

• A7( ena#les the insertion of a re&ister slice in

any channel at the cost of an additional cycle

latency

Trade"oF #etween latency and ma3imum fre@uency

• (t can #e advanta&eous to use

>irect and fast connection #etween a processor and

hi&h"performance memory

Simple re&ister slices to isolate a lon&er path to less

performance"critical peripherals




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Bacu,S(ides



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A Com,uter System

21

CPU

5ort'Brid3e

Sout'Brid3e

Main

Memory6##/2

8SB 68rontSide Bus

#M16#irect Media 18

ard dis

USB

PC1e card

1O devices

9ra,'ics card

A ) i ( 1O S t S ' ti



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A )y,ica( 1O System Sc'ematic6Sim,(i:ed

22

Memory Bus; 1O bus

CPU Core

Cac'e

MainMemory

#is

1OContro((er

9ra,'icsCard 5et"or

1nterru,ts

#is

1OContro((er

1OContro((er

MemoryContro((er

bus



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1O 1nterconnection

• A bus is a shared communication lin' A sin&le set of wires used to connect multiple components

• Composed of address #us2 data #us2 and control #us readwrite/

Advanta&es

• ;ersatile G new devices can #e added easily and can #e moved#etween computer systems that use the same #us standard

• ,ow cost G a sin&le set of wires is shared in multiple ways

>isadvanta&es

• Communication #ottlenec' G #us band"idt' limits the ma3imum (!t'rou3',ut

• The ma3imum #us speed is lar&ely limited #y

The (en3t' of the #us

The number of devices on the #us

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1O 1nterconnection 6Cont

• (! devices and interconnection lar&ely contri#ute tothe performance of computer system

• Traditionally2 parallel shared wires had have/ #eenused to connect (! devices

• As the cloc' fre@uency increases for communicatin&

with (! devices2 parallel shared wires suFer fromcloc' s'ew and interference amon& wires

• (ndustry transitioned from parallel shared #uses tohi&h"speed serial point"to"point interconnections

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)y,es o* Buses

• Processormemory bus

ront Side us S/2 proprietary #us• $eplaced #y HP( Huic'Path (nterconnect/ in (ntel

• $eplaced #y 0ypertransport in AM>

Short and hi&h speed

Matched to the memory system to ma3imie thememory"processor #andwidth

!ptimied for cache #loc' transfers

• Bac,(ane 6bacbone bus (ndustry standard

• e.&.2 PC(e3press

Allow processor2 memory and (! devices tocoe3ist on a sin&le #us

Used as an intermediary #us connectin& (!#usses to the processor"memory #us

• 1O bus (ndustry standard

• e.&.2 SATA2 US2 irewire

Usually is len&thy and slower

Ieeds to accommodate a wide ran&e of (!devices

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CPU

5ort'Brid3e

Sout'Brid3e

MainMemor

y6##/2

8SB

68rontSide Bus

#M1

6#irect Media 18

ard dis

USB

9ra,'ics card

Processormemorybus Bac,(ane bus

1O bus

o" #oes CPU Access 1O



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Memory S,ace

o" #oes CPU Access 1O#evices<

• All the (! devices have re&isters

implemented2 so softwarepro&rammers can use them to controlthe devices Then2 for pro&rammin&2 where and how

to write to or read fromJ

There are 4 ways to access (! devices• Memory"mapped (!

• (!"mapped (!

• Memoryma,,ed 1O (! device is mapped to a memory space

CPU &enerates a memory transaction toaccess (! device

To access (! device• (n M(PS2 use lw or sw instructions

• (n 3D+2 use mov instruction

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535

53

9L")/

Main Memory6%9B

536

)L")/

1O device

1O device

1O device



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o" CPU Accesses 1O #evices<

• 1Oma,,ed 1O

(! devices are mapped to (! space CPU &enerates (! transaction to access

(! device

To access (! device• (n 3D+2 there are in and out instructions.

• (n 3D+2 (! space is +9K

• To diFerentiate memory space and (!space2 there should #e hardwaresupport (SA support

• (n 3D+2 mov instruction for memory transactionand in,out instruction for (! transaction

Physical pin from processor indicatin& thetransaction type memory or (!/

• or e3ample2 the pin is driven to <)= formemory transaction or <5= for (! transaction

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535

1O S,ace

6=4KB in +>=

53

+9K")/

1O device

1O device

1O device

o" 1O Communicates "it'



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o" 1O Communicates "it'CPU<

• Po((in3

CPU periodically chec's the status of (! devices to determineits need for service

• CPU is totally in control

• Can waste a lot of CPU time due to speed diFerences

• 1nterru,t

(! device issues an interrupt to indicate that it needsattention

An (! interrupt is asynchronous wrt with respect to/instruction e3ecution

• (t is not associated with any instruction2 so doesnt prevent anyinstruction from completin&

• ?ou can pic' your own convenient point in the pipeline to handle theinterrupt

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#MA 6#irect Memory Access

• Typically2 movin& data from one place to another involve CPU

instructions ,oad lw/ from a location e.&. memory in an (! device/

Store sw/ to another location e.&. main memory/

Movin& a lar&e chun' of data with CPU instructions could ta'e a lar&e fractionof CPU time

• >MA has the a#ility to transfer lar&e #loc's of data direct(y tofromthe memory "it'out invo(vin3 t'e ,rocessor

). The processor initiates the >MA transfer #y supplyin& source and destinationaddresses2 the num#er of #ytes to transfer

4. The >MA controller mana&es the entire transfer possi#ly thousand of #ytesin len&th/2 ar#itratin& for the #us

6. -hen the >MA transfer is complete2 the >MA controller interrupts theprocessor to inform that the transfer is complete

• There may #e multiple >MA devices in one system

Processor and >MA controllers contend for #us cycles and for memory

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