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Memory organization of 8051
The 8051 microcontroller has 128 bytes of internal RAM and 4Kbytes of internal ROM memory. It uses the same addresses for code and data but accesses the correct memory based on whether an operation is for code or data. The 128 bytes of internal RAM are organized into 4 banks of 32 bytes each. External memory can be added if more memory is needed for program code or variable data storage. The document also provides information on interfacing external program and data memory with the 8051 microcontroller.
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Memory organization of 8051
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- 2. INTERNAL MEMORYINTERNAL MEMORY Afunctioning computer must have memory for program code bytes, commonly in ROM, and RAM memory for variable data that can be altered as the program runs 8051 has internal RAM (128 bytes) and ROM (4Kbytes) 8051 uses the same address but in different memories for code and data Internal circuitry access the correct memory based on the nature of the operation in progress Can add memory externally if needed
- 3. 8051 Internal RAMOrganisation8051 Internal RAM Organisation R7 R6 R5 R4 R3 R2 R1 R0 R7 R6 R5 R4 R3 R2 R1 R0 R7 R6 R5 R4 R3 R2 R1 R0 R7 R6 R5 R4 R3 R2 R1 R0 07 06 05 04 03 02 01 00 0F 0E 0D 0C 0B 0A 09 08 17 16 15 14 13 12 11 10 1F 1E 1D 1C 1B 1A 19 18 Bank0Bank1Bank2Bank3 27 26 25 24 23 22 21 20 2F 2E 2D 2C 2B 2A 29 28 7F 78 77 70 6F 68 67 60 5F 58 57 50 4F 48 47 40 3F 38 37 30 2F 28 27 20 1F 18 17 10 0F 08 07 00 30 7F Working Registers Bit Addressable General Purpose
- 4. Program Status Word(PSW)Program Status Word (PSW) Bank Select Bits, RS1, & RS0 to select 1 of 4 register bankBank Select Bits, RS1, & RS0 to select 1 of 4 register bank
- 5. Internal ROMInternal ROM InternalROM occupies the code address space from 0000H to 0FFFH (Size = 4K byte) Program addresses higher than 0FFFH will automatically fetch code bytes from external program memory Code bytes can also be fetched exclusively from an external memory by connecting the external access pin (EA) to ground
- 6. Interfacing with ExternalProgram MemoryInterfacing with External Program Memory
- 7. Interfacing with ExternalData MemoryInterfacing with External Data Memory
- 8. Read referenceReadreference The 8051 Microcontroller and Embedded Systems - Using Assembly and C, Mazidi • The 8051 Microcontroller – Hardware, Software and Interfacing, James W. Stewart • Microprocessor and Micro controllers – Prof. C.R.Sharma, Premier publishing house