Download to read offline
![Addressing Modes Register Indirect – the address of the source or destination is specified in registers Uses registers R0 or R1 for 8-bit address: mov psw, #0 ; use register bank 0 mov r0, #0x3C mov @r0, #3 ; memory at 3C gets #3 ; M[3C] 3 Uses DPTR register for 16-bit addresses: mov dptr, #0x9000 ; dptr 9000h movx a, @dptr ; a M[9000] Note that 9000 is an address in external memory](https://image.slidesharecdn.com/presentation1-241002235234-189593e9/75/Microcontroller-Introduction-and-the-various-features-18-2048.jpg)
![Addressing Modes Register Indexed Mode – source or destination address is the sum of the base address and the accumulator(Index) • Base address can be DPTR or PC mov dptr, #4000h mov a, #5 movc a, @a + dptr ;a M[4005]](https://image.slidesharecdn.com/presentation1-241002235234-189593e9/75/Microcontroller-Introduction-and-the-various-features-20-2048.jpg)
![Addressing Modes Register Indexed Mode continue • Base address can be DPTR or PC ORG 1000h 1000 mov a, #5 1002 movc a, @a + PC ;a M[1008] 1003 Nop • Table Lookup • MOVC only can read internal code memory PC](https://image.slidesharecdn.com/presentation1-241002235234-189593e9/75/Microcontroller-Introduction-and-the-various-features-21-2048.jpg)
Microcontroller Introduction and the various features
- 1. 8051 Internal BlockDiagram
- 3. 3 CM MOVC A,@A +DPTR ;A CM(A+DPTR) MOVC A,@A + PC ;A CM(A+PC) PC = PC(15..0) DPTR = DPTR(15..0)
- 4. 4 Data memory XM DM MOV A,62H MOVR1,#62H MOV A@R1 MOV A,0A2H MOV R1,#0A2H MOV A@R1
- 5.
- 6.
- 7.
- 8.
- 9. 9 Program Status Word(PSW) D0 D7 D6 D5 D4 D3 D2 - D0 PSW D0 CY AC F0 RS1 RS0 OV - P PSW • Carry flag (CY) • Is a dual-purpose. Carry out of bit 7 during add, or borrow into bit 7 during a subtract. • EX: MOV A, #FFH ADD A, #1 • What is the state of the carry flag and the content of the accumulator after execution of the following instruction sequence? MOV R5, #55H; MOV A, #0AAH; ADD A, R5; • Solution: • A=FFH and CY=0 (No Carry) A=00H and sets the carry flag in the PSW (ie CY=1).
- 10. 10 Program Status Word(PSW) D0 D7 D6 D5 D4 D3 D2 - D0 PSW D0 CY AC F0 RS1 RS0 OV - P PSW • Auxiliary Carry flag (AC) • When adding a BCD values, the AC is set if a carry was generated out of bit 3 into bit 4. • What is the state of the AC and the content of the accumulator after execution of the instruction sequence below? • MOV R5, #1; MOV A, #9; ADD A, R5; • Solution: A=10H (BCD) =1010 = 00010000B AC=1
- 11. 11 Program Status Word(PSW) D0 D7 D6 D5 D4 D3 D2 - D0 PSW D0 CY AC F0 RS1 RS0 OV - P PSW • Register bank select bit (RS1 and RS0) RS1 RS0 Register Bank # 0 0 0 0 1 1 1 0 2 1 1 3 • SETB RS1; CLR RS0; Register Bank 2 • SETB RS1 (= SETB 0D4H) • SETB RS0 (=SETB 0D3H)
- 12. 12 Program Status Word(PSW) D0 D7 D6 D5 D4 D3 D2 - D0 PSW D0 CY AC F0 RS1 RS0 OV - P PSW • Overflow Flag (OV) • When signed numbers are added or subtracted, software can examine this bit to determine if the result is in the proper range ( -128 < X < 127). • If X >=127 and X <=-128 OV=1 • MOV R7, #0FFH; MOV A, #0FH; ADD A, R7; • Solution • R7=11111111 (00000000+1=-00000001B=-1) • A=00001111 (15) • A=-1+15=14 =0EH< 127 OV=0 (No overflow)
- 13. 13 Program Status Word(PSW) D0 D7 D6 D5 D4 D3 D2 - D0 PSW D0 CY AC F0 RS1 RS0 OV - P PSW • Parity bit (P) • The P is set or cleared each machine cycle to establish even parity accumulator. • MOV A, #55H • A=01010101B numbers of 1-bit = 4 P=0
- 14. Addressing Modes Immediate Mode– specify data by its value mov A, #0 ;put 0 in the accumulator ;A = 00000000 mov R4, #11h ;put 11hex in the R4 register ;R4 = 00010001 mov B, #11 ;put 11 decimal in b register ;B = 00001011 mov DPTR,#7521h ;put 7521 hex in DPTR ;DPTR = 0111010100100001
- 15. Addressing Modes Register Addressing– either source or destination is one of CPU register MOV R0,A MOV A,R7 ADD A,R4 ADD A,R7 MOV DPTR,#25F5H MOV R5,DPL MOV R,DPH Note that MOV R4,R7 is incorrect
- 16. Addressing Modes Direct Mode– specify data by its 8-bit address Usually for 30h-7Fh of RAM Mov a, 70h ; copy contents of RAM at 70h to a Mov R0,40h ; copy contents of RAM at 70h to a Mov 56h,a ; put contents of a at 56h to a Mov 0D0h,a ; put contents of a into PSW
- 17. Addressing Modes Direct Mode– play with R0-R7 by direct address MOV A,4 MOV A,R4 MOV A,7 MOV A,R7 MOV 7,2 MOV R7,R6 MOV R2,#5 ;Put 5 in R2 MOV R2,5 ;Put content of RAM at 5 in R2
- 18. Addressing Modes Register Indirect– the address of the source or destination is specified in registers Uses registers R0 or R1 for 8-bit address: mov psw, #0 ; use register bank 0 mov r0, #0x3C mov @r0, #3 ; memory at 3C gets #3 ; M[3C] 3 Uses DPTR register for 16-bit addresses: mov dptr, #0x9000 ; dptr 9000h movx a, @dptr ; a M[9000] Note that 9000 is an address in external memory
- 19. Use Register Indirectto access upper RAM block (+8052)
- 20. Addressing Modes Register IndexedMode – source or destination address is the sum of the base address and the accumulator(Index) • Base address can be DPTR or PC mov dptr, #4000h mov a, #5 movc a, @a + dptr ;a M[4005]
- 21. Addressing Modes Register IndexedMode continue • Base address can be DPTR or PC ORG 1000h 1000 mov a, #5 1002 movc a, @a + PC ;a M[1008] 1003 Nop • Table Lookup • MOVC only can read internal code memory PC