1. Memory organization On- chip memory Off-chip memory
Internal memory
External Data memory
(upto 64KB) RAM
Internal SFRs
External Code memory
(upto 64KB) ROM
Internal ROM
Internal RAM
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Micro 8051

2. On-Chip Memory Internal RAM
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Micro 8051

3. 8051 CPU Registers A (Accumulator) B PSW (Program Status Word)
SP (Stack Pointer)
PC (Program Counter)
DPTR (Data Pointer)
Used in assembler instructions
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Micro 8051

4. General Purpose Register1F 18
Bank 3
4 Register Banks
Each bank has R0-R7
Selectable by PSW.2,3 17 10
Bank 2 0F 08
Bank 1 07 06 05 04 03 02 01 00 R7 R6 R5 R4 R3 R2 R1 R0
Bank 0
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Micro 8051

5. Bit Addressable Memory2F 2E 2D 2C 2B 2A 29 28
20h – 2Fh
(16 locations  8-bits = 128 bits) 7F 78 1A 10 0F 08 07 06 05 04 03 02 01 00 27 26 25 24 23 22 21 20
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Micro 8051

6. Summary of on-chip data memory (RAM)
MOV C, 67H ≡ MOV C, 2CH.7
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Micro 8051

7. Summary of on-chip data memory
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Micro 8051

8. Special Function Registers
DATA registers
CONTROL registers
Timers
Serial ports
Interrupt system
Etc.
Addresses 80h – FFh
Direct Addressing used to access SFRs
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Micro 8051

9. Port 0 with external pull-up resistors
8751
8951
Vcc
10 K
Port 0
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Micro 8051

10. How the ports can be used as input?
Port 0 as input
Port must be programmed by writing 1 to all the bits.
E.g
REPEAT: MOV A, #0FFH
MOV P0, A
MOV A, P0
MOV P1, A
SJMP REPEAT
Similarly for Port 1 when used as input.
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Micro 8051

11. Continues… Port 3 Alternate functions: P3.0 RxD Serial Input line
P TxD Serial Output line
P INT External interrupt 0
P INT External interrupt 1
P T Timer0 External input
P T Timer1 External input
P WR External data memory WR strobe
P RD External data memory RD strobe
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Micro 8051

12. Address Multiplexing for External Memory (code)
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13. 18-Nov-18
Micro 8051

14. Stack Concepts

15. Continues…

16. Examples of Push operation

17. Examples of POP operation