Page 101 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Unit 6: The 8085 Microprocessor Architecture

Notes
Questions:
1. Explain the Virtual 8085 tool.

2. How to make easier the learning process of the 8085 assembly language?
6.3 Summary

• In 8085 the bus structure is multiplexed with 8 lower address lines and requires only 5 V as
single power supply.
• The TRAP interrupt has the highest priority and is a non-maskable interrupt.
• 8085A has eight unidirectional (A to A ) signal lines corresponding to; pin 21 to pin 28.
8 15
• 8085A store only one byte of data. It is used for temporary storage of instructions, data or
address.
• Program Counter (PC) is common to all microprocessors and is called a memory pointer.

6.4 Keywords

• Immediate Addressing: This is the technique of addressing by which the data to be operated
upon by the CPU is given to processor without using memory locations during transfer
• MAR: Memory chips have a memory address register (MAR), also called the address latch.
This stores the address from the address bus and is connected to the memory chip.
• SID: Serial input data (SID) pin is a 1-bit input port of the 8085A
• SOD: The Serial Output Data (SOD) line provides a 1-bit output port on the 8085A
• SP: Stack pointer is a dedicated 2-byte (16-bit) register. A stack is set of memory locations in
the RAM area, which is specifically used to store certain temporary data. The starting address
of the stack area is stored in the 16-bit CPU register called the stack pointer
1. Write fetching instruction opcode of 8085.
2. Show the read cycle of 8085 microprocessor.

6.5 Self-Assessment Questions

1. The ........................ instruction is essential to output data serially from the SOD line.

(a) SIM (b) RESET

(c) RST (d) None of these
2. ........................ is commonly used to connect the output devices to the microprocessor.
(a) Address bus (b) Latch

(c) Register (d) Buffer
3. 8085A has ........................ signal lines corresponding to; pin 21 to pin 28.
(a) five unidirectional (b) six unidirectional
(c) seven unidirectional (d) eight unidirectional
4. A stack is set of memory locations in the RAM area, which is specifically used to store
certain.
(a) Permanent data (b) Secondary data
(c) Temporary data (d) All of these

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