8085 Programming Model
- 6 general purpose registers to store 8-bit data B, C, D, E, H & L.
- Can be combined as register pairs – BC, DE, and HL to perform 16-bit operations.
- Used to store or copy data using data copy instructions.
- 8 – bit register, identified as A
- Part of ALU
- Used to store 8-bit data to perform arithmetic & logical operations.
- The result of the operation is stored in it.
Flag Register in 8085 Programming Model
- ALU has 5 Flag Register that set/reset after an operation according to data conditions of the result in accumulator & other registers.
- Moreover, Helpful in decision-making process of Microprocessor
- Also, Conditions tested through software instructions For e.g.
- JC (Jump on Carrying) implemented to change the sequence of the program when CY set.
- 16-bit registers used to hold memory addresses.
- Moreover, Size is 16-bits because memory addresses 16-bits.
- The microprocessor uses PC register to sequence the execution of instructions.
- Also, Its function to point to the memory address from which next byte is to fetched.
- When a byte is fetched, PC is incremented by 1 to point to next memory location.
- Used as memory pointer
- Points to the memory location in R/W memory, called Stack.
- The beginning of stack defined by loading a 16-bit address in the stack pointer.
What is Instruction Cycle?
- Instruction Cycle defined as the time required to complete execution of an instruction.
- Moreover, 8085 instruction cycle consists of 1 to 6 Machine Cycles or 1 to 6 operations.
What is Machine Cycle?
- Machine Cycle defined as the time required by the microprocessor to complete operation of accessing memory device or I/O device.
- Also, This cycle may consist 3 to 6 T-states.
- The basic microprocessor operation such as reading a byte from I/O port or writing a byte to memory called as the machine cycle.