GENERAL PURPOSE RAM FOR MICROCONTROLLER
- M/c uses separate spaces for data and code.
- Internal memory of m/c consists of on chip code memory and data memory which is “RAM”.
- On chip RAM consist of general purpose registers, bit addressable locations and special purpose registers.
- General purpose RAM starts from 30 H and ends at 7FH.
- Any location of RAM can be addressed freely using direct or indirect addressing modes.
- For example to read the contents of location 5FH into accumulator we use instruction
MOV A, 5FH
- This is direct addressing and instruction will copy all the contents of location 5FH into accumulator.
- RAM can also be assessed by indirect addressing mode for example
MOV R0, #5FH
- First instruction is immediate addressing and will load value 5FH in register R0.
- Second instruction represents indirect addressing mode and will copy data contents pointes by register R0.