Question

The total number of memory accesses involved (inclusive of the opcode fetch) when an 8085 microprocessor executes the instruction lda 2003h is

Answer 1

• The total number of memory accesses involved (inclusive of the opcode fetch) when an 8085 microprocessor executes the instruction LDA 2003h is 3.
• LDA is a stands for LoaD Accumulator. Where the accumulator loads the contents from the memory.
• The accumulator will load 8 bit data from a 16 bit memory address (eg: 2003). Hence LDA operation occupies 3 bytes in the memory. The first byte is for opcode, second byte for Low order Byte of the address (eg: 03) and third byte for High order Byte of the address (eg: 20)
• To perform this operations 4 machine cycles are required - Opcode Fetch, Memory Read (data), Memory Read (lower order byte address), Memory Read (higher order byte address)