Addressing modes 8085
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The document discusses the different addressing modes of the 8085 microprocessor. There are four addressing modes: immediate addressing where data is present in the instruction, register addressing where data is provided through registers, direct addressing used to accept data from outside devices, and indirect addressing where the processor calculates an effective address from which to obtain the actual data address.
Addressing modes 8085
- 1. 8085 Addressing Modes Varun Sukheja Student 6th semester Department of Computer Science & Engineering Lakshmi Narain College of Technology and Science
- 2. The 8085 Addressing Modes The instructions MOV B, A or MVI A, 82H are to copy data from a source into a destination. In these instructions the source can be a register, an input port, or an 8-bit number (00H to FFH). Similarly, a destination can be a register or an output port. The sources and destination are operands. The various formats for specifying operands are called the ADDRESSING MODES. For 8085, they are: • 1. Immediate addressing. • 2. Register addressing. • 3. Direct addressing. • 4. Indirect addressing.
- 3. •Immediate addressing • Data is present in the instruction. Load the immediate data to the destination provided. • Example: MVI R, data • MVI A,05(H) • LXI H,0050(H)
- 4. •Register addressing • Data is provided through the registers. • Example: MOV Rd, Rs • MOV B,C • ADD B
- 5. •Direct addressing • Used to accept data from outside devices to store in the accumulator or send the data stored in the accumulator to the outside device. • Accept the data from the port 00H and store them into the accumulator or Send the data from the accumulator to the port 01H. • Example: IN 00H • OUT 01H • LDA 0208(H)
- 6. •Indirect Addressing • This means that the Effective Address is calculated by the processor. And the contents of the address (and the one following) is used to form a second address. • The second address is where the data is stored. • Note that this requires several memory accesses; two accesses to retrieve the 16-bit address and a further access (or accesses) to retrieve the data which is to be loaded into the register. • LDAX B