Mechatronics UNIT 2.pptx
- 1. Unit - 2 8085 MICROPROCESSOR AND 8051 MICROCONTROLLER
- 2. Internal Architecture of 8085
- 3. Internal Architecture of 8085 Address bus : • The address bus is a group of 16 lines generally identified as A0 to A15. • The address bus is unidirectional : bits flow in one direction-from the MPU to peripheral devices. • The MPU (Memory Protection Unit) uses the address bus to perform the first function : identifying a peripheral or a memory location.
- 4. Internal Architecture of 8085 Data bus : • The data bus is a group of eight lines used for data flow. • These lines are bi-directional - data flow in both directions between the MPU and • memory and peripheral devices. • The MPU uses the data bus to perform the second function: transferring binary information. Control bus : • The control bus carries synchronization signals and providing timing signals. • The MPU generates specific control signals for every operation it performs. • These signals are used to identify a device type with which the MPU wants to communicate.
- 5. Internal Architecture of 8085 Registers of 8085 : • The 8085 have six general - purpose registers to store 8-bit data during program execution. • These registers are identified as B, C, D, E, H, and L. • They can be combined as register pairs - BC, DE, and HL - to perform some 16 - bit operations. Accumulator (A) : • The accumulator is an 8 - bit register that is part of the arithmetic/logic unit (ALU). • This register is used to store 8-bit data and to perform arithmetic and logical operations. • The result of an operation is stored in the accumulator.
- 6. Internal Architecture of 8085 Flags : • The ALU includes five flip-flops that are set or reset according to the result of an • operation. • The microprocessor uses the flags for testing the data conditions. • They are Zero (Z), Carry (CY), Sign (S), Parity (P) and Auxiliary Carry (AC) flags. • The most commonly used flags are Sign, Zero and Carry. • The bit position for the flags in flag register is Accumulator (A) Sign flag (S) : • After execution of any arithmetic and logical operation, if D7 of the result is 1, the sign flag is set. • If D, is 1, the number will be viewed as negative number. If D7 is 0, the number will be viewed as positive number. Zero flag (z) : • If the result of arithmetic and logical operation is zero, then zero flag is set, otherwise it is reset.
- 7. Internal Architecture of 8085 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.
- 8. Internal Architecture of 8085 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). 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.
- 9. Internal Architecture of 8085 Timing and Control Unit : • It has three control signals ALE (Address Enable Latch), RD (Active low) and WR (Active low) and three status signals IO/M(Active low). • ALE is used for provide control signal to synchronize the components of • microprocessor and timing for instruction to perform the operation. • RD (Active low) and WR (Active low) are used to indicate whether the operation is reading the data from memory or writing the data into memory respectively. • IO/M (Active low) is used to indicate whether the operation is belongs to the memory or peripherals.
- 10. Internal Architecture of 8085 Interrupt Control Unit : • It receives hardware interrupt signals and sends an acknowledgement for receiving the interrupt signal.