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Addressing modes• Determines how one access memory

• Addressing refers to means to specify location of

operands for instructions  - types of addressing are called addressing modes

- operands may be input operands for the operation aswell as results of the operation

• Addressing modes supported by the TMS320C!"include

  register-indirect#  inde"ed register-indirect#

and  modulo addressing $circular addressing%&

'mmediate data is also supported&

•

  The TMS320C!" does not support modulo addressingfor (-bit data&

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 ADD .L1 -13,A1,A6 

(implied)  ADD .L1 A7,A6,A7 

not supported

LDW .L1 *A5++[8,A1

 

• 'mmediate

 – The operand is part ofthe instruction

• )egister

 – The operand is speci*edin a register

• Direct

 – The address of theoperand is part of theinstruction $added toimply memory page%

• 'ndirect

 – The address of theoperand is stored in aregister

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Register-Indirect Addressing

•  +perand is located in memory address stored in a

register•   Special group of registers can be used to store

addresses

  $address registers%

•   Most important addressing mode in DS,s•  .cient from instruction set point of /iew

•   ew bits are needed to indicate address of operand

• 32 registers$A0-A1#0-1% are used as pointers

• 'ndirect addressing uses 4*5 in con6unction with one of

the 32 registers

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• 1& *) 7 register ) contains address of a memorylocation

•   where a data /alue is stored• 2& *)88 $d% - register ) contains memory address

•   - after the memory address is used# ) is

•   postincremented such that new address is)81 if d91

•   - double minus $- -% update the address by

d-1•

3.  * 88 )$d% - address is preincremented or o:set by d•   - current address is )8d or )-d•

4.  * 8 )$d% - address is preincremented by d# such that

the current address is )8d•   - howe/er ) pre increments withoutmodi*cation

•   - unli;e pre/ious case# ) is not updated ormodi*ed

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Delay <ine implemented with

shifting of sample

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Delay <ine pointer manipulationusing Circular Addressing

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Circular addressing• Circular addressing is used to create a circular bu:er

•

u:er is created in hardware and is /ery useful forapplications li;e digital *ltering

•  This addressing mode in con6unction with circular bu:erupdates samples by shifting data without creatingo/erhead as in direct shifting

•

=hen pointer reaches bottom location# and whenincremented the pointer is automatically wrapped aroundto the top location&

•  Two independent bu:ers are a/ailable using >0 and >1within the AM) register

• )egisters A(-A! and (-! in con6unction with &D unit canbe used as pointers

• M?C $mo/e constant% is the only instruction to access AM)and other control registers

Ci l :

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Circular u:er

At the beginning of eachsample period#a new sample will be readinto the circular

bu:er#o/erwriting the oldestsample&

 The newest sample "$n% willbe stored at the memory

location pointed at byau"iliary register A)$i%&

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•  The need of processing the digital signals in real time#e/ol/es the concept of Circular u:ering&

• Circular bu:ers are used to store the most recent

/alues of a continually updated signal&

• Circular bu:ering allows processors to access a bloc;of data se@uentially and then automatically wraparound to the beginning address e"actly the patternused to access coe.cients in ') *lter&

• Circular bu:ering also /ery helpful in implementing*rst-in# *rst-out bu:ers# commonly used for '+ and for

') delay lines&• Most DS, 'mplement Circular addressing in hardware

in order to conser/e memory and minimiBing softwareo/erhead&

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 (AMR)

•

or each of the eight registers $A(7A!# (7!% that canperform linear or circular addressing# the addressingmode register $AM)% speci*es the addressing mode&

•

A 2-bit *eld for each register selects the addressmodi*cation mode linear $the default% or circularmode&

•

=ith circular addressing# the *eld also speci*es which> $bloc; siBe% *eld to use for a circular bu:er&

• 'n addition# the bu:er must be aligned on a byteboundary e@ual to the bloc; siBe&

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  AMR mode and description

Mode description00 for linear addressing01 for circular addressing using >0•   or circular addressing using >1•   reser/ed

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Block size = 2!" #$tes