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Features and addressing modes of 8085

Short answer

Features: 8-bit data bus, 16-bit address bus for 64 KB memory; single +5 V supply with on-chip clock, 3 MHz; five interrupts plus SID/SOD and 256 I/O ports. Addressing modes are immediate, register, direct, register indirect, and implied, with examples MVI A,45H; MOV A,B; LDA 2050H; MOV A,M; CMA.

Write any three features of 8085 microprocessor. Explain the addressing modes of 8085 with example.

Features of 8085

  1. 8-bit microprocessor with 8-bit data bus and 16-bit address bus (addresses 64 KB memory).
  2. Single +5 V supply and on-chip clock generator; operates at 3 MHz (internal clock = crystal frequency / 2).
  3. Has 5 hardware interrupts (TRAP, RST7.5, RST6.5, RST5.5, INTR), serial I/O lines (SID, SOD), and addresses 256 input and 256 output ports.

(Others: multiplexed address/data bus AD0-AD7, 74 instructions, 40-pin DIP, HOLD/HLDA DMA support.)

Addressing modes

The way in which the operand of an instruction is specified.

  1. Immediate: data is in the instruction itself. MVI A,45H (A <- 45H), LXI SP,2FFFH.
  2. Register: the operand is in a register. MOV A,B (A <- B), ADD C.
  3. Direct: the instruction has the 16-bit memory address (or 8-bit port address) of the operand. LDA 2050H (A <- M[2050H]), STA 3000H, IN 80H.
  4. Register indirect: a register pair holds the memory address. MOV A,M (address in HL), LDAX B (address in BC), STAX D.
  5. Implied: the opcode itself says which register holds the operand, so no operand is written. CMA (complement A), RAL, DAA, STC.

✓ Answer checked by Claude Opus 5.5 (high effort)

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