Architechture of 8085 (Contd..)
Temporary Register: It is used to hold the data during the arithmetic and logical operations.
Instruction Register: When an instruction is fetched from the memory, it is loaded in the instruction register.
Instruction Decoder: It gets the instruction from the instruction register and decodes the instruction. It identifies the instruction to be performed.
Serial I/O Control: It has two control signals named SID and SOD for serial data transmission.
Arithmetic and Logic Unit (ALU):
- It is used to perform the arithmetic operations like addition, subtraction, multiplication, division, increment and decrement and logical operations like AND, OR and EX-OR.
- It receives the data from accumulator and registers.
- According to the result it set or reset the flags.
Program Counter (PC):
- This 16-bit register sequencing the execution of instructions.
- It is a memory pointer. Memory locations have 16-bit addresses, and that is why this is a 16-bit register.
- The function of the program counter is to point to the memory address of the next instruction to be executed.
- When an opcode is being fetched, the program counter is incremented by one to point to the next memory location.
Stack Pointer (Sp):
- The stack pointer is also a 16-bit register used as a memory pointer.
- It points to a memory location in R/W memory, called the stack.
- The beginning of the stack is defined by loading a 16-bit address in the stack pointer (register).
