Architecture of 8085 Microprocessor
8085 is a 8-bit microprocessor. Here the data is usually 8 bit and the address is 16 bit. Let’s analyze the each and every components of 8085 microprocessor.
1) Register section
2) ALU
3) The buses
4) Timing & Control unit
1) Register section:
It consists of number of registers for storing data and addresses. It can be of two types:
a) General purpose registers
b) Special purpose registers
General purpose registers are used for temporary storage of data or address during execution. They are B, C, D, E, H and L. They are all 8 bit registers. So, to store 16 bit data we have to form a register pair like: BC, DE or HL.
Special purpose registers:
The following registers come under this category and each performing a special function.
Accumulator (A) – It is a 8 bit register which is used for storing the operands/data during execution.
Program counter (PC) – It is a 16 bit register used to store the memory address of the next instruction to be executed.
Index register – This is used for addressing index addressing mode.
Status register – It stores the present status of the microprocessor after any arithmetic and logical operation. It records any occurrence of carry, auxiliary carry, sign, zero and odd/even parity.
Stack pointer – It is a 16 bit register used to initialize the stack.
Instruction register – It is a 8 bit register that stores the instruction fetched from memory
2) Arithmetic and Logical Unit (ALU):
It performs arithmetic and logical operations. Addition, subtraction, multiplication, division, AND, OR, XOR, NOT, shift and rotate operations are done by ALU.
3) The Buses:
It is the interface section for communication between processor and external devices. There are 3 buses
a) Address bus – It carries the address of the instruction. It is 16 bit wide and unidirectional.
b) Data bus – It carries data between external devices and processor. It is 8 bit wide and bidirectional.
c) Control bus – It is used to send control signals to different units of microprocessor.
4) Timing & Control unit:
It generates the clock signals and control signals for communication between processor and peripheral devices.
Like it on Facebook, Tweet it or share this article on other bookmarking websites.