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Why do we need external memory in the 8051?
Now that we have understood the on-chip memory organization and RAM structure of 8051 let us look at how to interface additional external Program Memory and Data Memory to the microcontroller. Why do we need external memory, though? The 8051 has on-chip RAM and ROM to store the temporary variables and the program code, respectively.
How is the MOVX instruction used in the 8051?
MOVX Instruction The 8051 microcontroller in most cases has an on-chip 4K flash memory, but due to its 16-bit address bus, it can access 64k memory locations. Due to this reason, the 8051 can be interfaced with external memory using ports 0 and 2. To access data in this external memory, the MOVX instruction is used
Where are the instructions stored in the 8051 microcontroller?
In 8051 Microcontroller, the code or instructions to be executed are stored in the Program Memory, which is also called as the ROM of the Microcontroller. The original 8051 Microcontroller by Intel has 4KB of internal ROM.
What are the data transfer instructions in 8051?
Data Transfer instructions in 8051 Data Transfer instructions in 8051 Any instruction given to the microcontroller contains two parts: an opcode and an operand. The opcode is responsible for telling the microcontroller what to do, whereas the operand holds the data on which the operations are to be performed.
How to move data to / from external Memor?
For e.g. if you want to copy byte (i.e. 8 bit) data stored at 1500h in your external memory. You’d write : Also, keep in mind that dptr (data pointer register) is actuality combination of two 8-bit special function registers, dph and dpl (having addresses 83h and 82h, in internal RAM respectively).
How does MOVX move a byte to external memory?
Description: MOVX moves a byte to or from External Memory into or from the Accumulator. If operand1 is @DPTR, the Accumulator is moved to the 16-bit External Memory address indicated by DPTR. This instruction uses both P0 (port 0) and P2 (port 2) to output the 16-bit address and data.