Handout 2 Digital System Engineering (EE-390) (Ref: Text book and KFUPM Online course of EE-390) (Remember to solve all the related examples, exercises problems as given in the Syllabus)
MOV Statement 0202 01 00 IP CS SS DS ES AX BX CX DX SP BP SI DI SR Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0200 0100 XX P.A’s 00000 01200 8C MOV DX, CS 01201 CA 01202 XX Next Instruction 01203 FFFFF 0202 01 00
Addressing Modes Accumulator
A) Register Operand Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 02F0 0120 XX 1B D7 P.A’s 00000 014F0 8B MOV AX, BX 014F1 C3 014F2 XX Next Instruction 014F3 FFFFF 02F2 1B D7
A) Register Operand Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0260 45A2 1B D7 XX P.A’s 00000 45C80 8B MOV DL, BH 45C81 C3 45C82 XX Next Instruction 45C83 FFFFF 0262 1B
B) Immediate Operand Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0400 0210 XX P.A’s 00000 02500 B8 MOV AX, 4A1FH 02501 1F 02502 4A 02503 XX Next Instruction FFFFF 0403 4A 1F
B) Immediate Operand Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0400 0210 XX P.A’s 00000 02500 B6 MOV DH, 28H 02501 28 02502 XX Next Instruction FFFFF 0402 28 XX
Valid and Invalid Instructions MOV CL, AH VALID MOV CX, SP VALID MOV CH, DX INVALID MOV 15H, AL INVALID MOV CL, 1234H INVALID MOV IP, CX INVALID MOV CS, DS INVALID MOV CL, 234H INVALID
C) Memory Operand Addressing Mode 1) Direct Memory Addressing 2) Indirect Memory Addressing a) Register Indirect Addressing b) Based Addressing c) Indexed Addressing d) Based-Indexed Addressing
C) Memory Operand Addressing Mode PA = Segment Base Address (SBA) : Effective Address (EA) = SBA : EA EA (called Effective or Offset) is EA = Base + Index + Displacement PA = SBA : Base + Index + Displacement CS SS DS ES PA = : + + BX BP SI DI 8-bit displacement 16-bit displacement
1) Direct Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 6500 XX P.A’s 00000 03210 8B MOV CX, [52F1H] 03211 0E 03212 F1 03213 52 03214 XX Next Instruction 6A2F1 = DS:52F1 3F 6A2F2= DS:52F2 D2 FFFFF 0012 Code segment D2 3F data segment
1) Direct Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 6500 XX P.A’s 00000 03210 8A MOV CH, [52F1H] 03211 2E 03212 F1 03213 52 03214 XX Next Instruction 6500 : 52F1 = DS : 52F1 3F FFFFF 0014 3F XX
1) Direct Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 6500 52 XX P.A’s 00000 03210 88 MOV [52F1H], CH 03211 2E 03212 F1 03213 52 03214 XX Next Instruction 6500 : 52F1 = DS : 52F1 FFFFF 0014 52
2) Register Indirect Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 6500 XX 0528 P.A’s 00000 03210 8B MOV CX, [SI] 03211 1C 03212 XX Next Instruction 03213 03214 6500 : 0528 = DS : SI 5D 6500 : 0529 = DS : SI + 1 CA FFFFF 0012 CA 5D
2) Register Indirect Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 6500 XX 0528 P.A’s 00000 03210 8A MOV CL, [SI] 03211 0C 03212 XX Next Instruction 03213 03214 6500 : 0528 = DS : SI 5D FFFFF 0012 XX 5D
NOTE By default, using a direct address as [1FA4H], or a register indirect address as [SI] or [DI] assumes you are accessing the DATA SEGMENT. MOV AX, [1FA4H] MOV AX, DS:[1FA4H] To access any other segment, use the “SEGMENT OVERIDE PREFIX” as MOV AX, CS:[1FA4H] MOV SS:[DI] , AX
3) Based Addressing Mode Base Register Points to first address of data (Constant) Displacement Contains number of bytes above base register where data of interest exists (Variable) When Base Register is BX PA = DS : BX + Displacement When Base Register is BP PA = SS : BP + Displacement These are default segments and Segment-Override Prefix changes them
3) Based Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 2577 6500 XX 12 10 15F8 P.A’s 00000 03210 8A MOV AL, [BX] + 2F10H 03211 87 03212 10 03213 2F 03214 XX Next Instruction 6500 : 1210 + 2F10 5D FFFFF 0014 XX 5D
3) Based Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 2577 6500 XX 12 10 15F8 P.A’s 00000 03210 8A MOV AL, [BP] + 2F10H 03211 86 03212 10 03213 2F 03214 XX Next Instruction 2577 : 15F8 + 2F10 5D FFFFF 0014 XX 5D
4) Indexed Addressing Mode Displacement Points to first address of data (Constant) Index Register Contains number of bytes above Displacement where data of interest exists (Variable) When Index Register is SI PA = DS : SI + Displacement When Base Register is DI PA = DS : DI + Displacement These are default segments and Segment-Override Prefix changes them
4) Indexed Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 2577 523C XX 76FF P.A’s 00000 03210 8A MOV AL, [SI] + 2F10H 03211 84 03212 10 03213 2F 03214 XX Next Instruction 523C : 76FF + 2F10 99 FFFFF 0014 XX 99
4) Indexed Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 2577 766A 12 10 8DA5 P.A’s 00000 03210 89 MOV [DI] + 2F10H, BX 03211 9C 03212 10 03213 2F 03214 XX Next Instruction 766A : 8DA5 + 2F10 766A : 8DA5 + 2F10 + 1 FFFFF 0014 10 12
5) Based-Indexed Addressing Mode Displacement Points to first address of data (Constant) Base Register Contains Matrix Column Number (Variable) Index Register Contains Matrix Row Number (Variable) Regardless of using SI or DI When Base Register is BX PA = DS : BX + (SI or DI) + Displacement When Base Register is BP PA = SS : BP + (SI or DI) + Displacement These are default segments and Segment-Override Prefix changes them
5) Based-Indexed Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 2577 523C XX 12 34 76FF P.A’s 00000 03210 8A MOV AL, [BX][SI] + 2F10H 03211 80 03212 10 03213 2F 03214 XX Next Instruction 523C : 1234 + 76FF + 2F10 99 FFFFF 0014 XX 99
5) Based-Indexed Addressing Mode Mem. contents IP CS SS DS ES AX BX CX DX SP BP SI DI SR 0010 0320 2577 523C FF 77 12 34 76FF P.A’s 00000 03210 89 MOV [BP][SI] + 2F10H, AX 03211 82 03212 10 03213 2F 03214 XX Next Instruction 2577 : 1234 + 76FF + 2F10 FFFFF 0014 FF 77