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+5 votes

"The Address Part of the Index Addressing mode Instruction must  set to zero,to behave like Register Indirect Mode Instruction"

asked in CO and Architecture by Loyal (8.4k points)
edited by | 238 views
  1. Index mode X(Ri)   EA=[Ri]+X
  2. Register indirect  Ri  EA=[Ri]  no they are not valid if you put index zero then i think valid

1 Answer

+4 votes

Yes, it is a valid statement, if Indexed address holds 0 in place of the base address and then this 0 is added with index register value then it acts similarly as if we are having register address in the instruction.

EA in Indexed Mode = M[base address from Instruction + Index register displacement] => M[0 + index register] => M[index register] (here base address is in instruction and Index register keeps displacement value which keep chnaging)

(Now here the displacement if got added to a base != 0(but some memory address) then it gives a address, also displacement if got added to base =0 is again address ) 

EA in Register Indirect = M[value in register] (Here register address is in Instruction)

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