Draw 8085 register based structure microprocessor & define the registers.

Accumulator register:

The accumulator register is an 8bit register that is a part of the arithmetic/

Logic unit (ALU):
This register used to store 8-bit data and in performing arithmetic and logical

Operations:

Flag register: 
The ALU includes five flip-flops that are set or reset according to data conditions in the

accumulator and other registers. There are five different types of data conditions:

1. Zero flag

2. Carry flag

3. Sign flag

4. Parity flag

5. Auxiliary carry flag.

Stack Pointer: 
The stack pointer is a 16-bit register used as a memory pointer, it points to a memory

location in read or write memory.

Program Counter: 
This 16-bit register is a memory pointer. Memory location has 16-bit address and

that is why this a 16-bit register.

Flag Register In Microprocessor

– 8 bit register
– shows the status of the microprocessor before/after an operation
– S (sign flag), Z (zero flag), AC (auxillary carry flag), P (parity flag) & CY (carry flag)

Flag Register In Microprocessor

Sign Flag:
• Used for indicating the sign of the data in the accumulator
• The sign flag is set if negative (1 – negative)
• The sign flag is reset if positive (0 –positive)

Zero Flag:
 – Is set if result obtained after an operation is 0
 – Is set following an increment or decrement operation of that register

Zero Flag

 Carry Flag:
– Is set if there is a carry or borrow from arithmetic operation            

Carry Flag:

Auxiliary Carry Flag: – Is set if there is a carry out of bit 3

Parity Flag:
– Is set if parity is even
– Is cleared if parity is odd                      

Architecture of Intel 8085 Microprocessor

Intel 8085 Microprocessor

• Microprocessor consists of:

– Control unit: control microprocessor operations.
– ALU: performs data processing function.
– Registers: provide storage internal to CPU.
– Interrupts
– Internal data bus

Architecture of Intel 8085 Microprocessor

Differences between Microprocessor, Microcomputer and Microcontroller

Differences between Microprocessor, Microcomputer and Microcontroller:

Microcomputer – a computer with a microprocessor as its CPU. Includes memory, I/O etc.

Microprocessor – silicon chip which includes ALU, register circuits & control circuits

Microcontroller – silicon chip which includes microprocessor, memory & I/O in a single package.