8085 Microprocessor S Senthil Kumar Dept of Aero

8085 Microprocessor S. Senthil Kumar, Dept. of Aero, KCT

8085 A Pin diagram and Signals

8085 Architecture

8085 Programmable Registers

8085 Bus Structure

8085 Microcomputer based Memory

8085 Microcomputer based Memory

Memory – 4 x 4 -bit Register (single chip)

Memory – 4 x 8 -bit Register (one chip and two chips)

Memory – 4 x 4 -bit Register (two chips and chip select)

Memory – 4 x 4 -bit Register (two chips and 4 address lines)

R/W Memory model and ROM model (Memory Chip)

Memory chip with 256 registers (256 bytes of memory)

Memory Map Ø The memory map is a picture representation of the address range and shows where the different memory chips are located within the address range.

Generation of Control Signals for Memory and I/O

Functions performed by 8085 Ø Microprocessor-initiated operations • Memory Read: Reads data (or instructions) from memory • Memory Write: Writes data (or instructions) into memory • I/O Read: Accepts data from input devices • I/O Write: Sends data to output devices Ø Internal operations • Store 8 -bit data • Perform arithmetic and logical operations • Test for conditions • Sequence the execution of instructions • Store data temporarily during execution in the defined R/W memory locations called stack Ø Peripheral (or externally initiated) operations • Reset, Interrupt, Ready, Hold

Instruction Cycle, Machine Cycle and T-State

8085 Instruction Fetch operation (Opcode Fetch – 4 T-states)

Opcode Fetch (4 T-states) – Timing Diagram

8085 – Demultiplexing the Bus AD 7 -AD 0

8085 Memory Read operation

Memory Read machine cycle – Timing Diagram

Memory Write machine cycle – Timing Diagram

I/O Read machine cycle – Timing Diagram

I/O Write machine cycle – Timing Diagram