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Basics 8085

TitleBasic-8085-microprocessor-architecture-functional blocks-Register-stack-pointer-ProgramCounter-ALU-Serial-I/O-Control
UniversityMumbai University
SubjectMicroprocessor and Microcontroller-I
ModuleBasics 8085
Total Lecture : 4 Remark :Easy, forms the basic of the subject. Understanding is very important
Module Brief

8085 was developed & manufactured by Intel corp. It took the place of 8080.

  1. It is a 8 bit microprocessor.
  2. It has 3Mhz speed.
  3. The 8085 microprocessor family can address 64K bytes of memory which is used for both code space and data space.
  4. 8085 can access up to 256 I/O devices.
  5. Memory is accessed by 20 pins.
  6. 8 address high pins and 8 pins  are used both for the 8 address low signals and for the 8 data signals.4 pins are used for control purpose.
  7. 8085 requires only a +5V power supply.

This microprocessor has seven 8-bit registers named A, B, C, D, E, H, and L, where A is the 8-bit accumulator and the other six can be used as independent byte-registers or as three 16-bit register pairs, BC, DE, and HL.

Stack Pointer (Sp):-

1.The stack pointer is also a 16-bit register used as a memory pointer.

2.It points to a memory location in R/W memory, called the stack.
3.The beginning of the stack is defined by loading a 16-bit address in the stack pointer (register).

Program Counter (PC):-

1.This 16-bit register sequencing the execution of instructions.

2.It is a memory pointer. Memory locations have 16-bit addresses, and that is why this is a 16-bit register.
3.The function of the program counter is to point to the memory address of the next instruction to be executed.

4.When an opcode is being fetched, the program counter is incremented by one to point to the next memory location.

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.

Other Internal blocks:

Arithmetic and Logic Unit (ALU):

 1.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.

2.It receives the data from accumulator and registers.
3.According to the result it set or reset the flags.

 Serial I/O Control: It has two control signals named SID and SOD for serial data transmission

Timing and Control unit:

1.It has three control signals ALE, RD (Active low) and WR (Active low) and three status signals IO/M(Active low), S0 and S1. 

2.ALE is used for provide control signal to synchronize the components of microprocessor and timing for instruction to perform the operation.
3.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.


Interrupt Control Unit:

:-It receives hardware interrupt signals and sends an acknowledgement for receiving the interrupt signal.

Expert Remark Subtopic: Features & block diagram
All blocks
Flag register
Google Best Link 1.http://www.8085projects.info/p age/8085-THE-COMPLETE-DETAILS. aspx
2.http://www.vijayendrasingh.com /8085.html
3.http://www.brighthub.com/engin eering/electrical/articles/512 29.aspx
4.http://en.wikipedia.org/wiki/I ntel_8085
5.http://www.scribd.com/doc/2083 8382/Microprocessor-8085-notes
6.http://www.cpu-world.com/Arch/ 8085.html
Tags8085, ALU, Microprocessor, Mumbai University 8085 basic notes, Microprocessor Features, Timing and control units, 8085 Registers, Internal Structure of 8085, 8085 Interrupts, Ready 8085, Hold 8085, 8085 Flag

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