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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"

in CO and Architecture by Loyal (8.5k points)
edited by | 250 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)

by (139 points)
edited by

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