Question

1.-¿which is why the control of electronic devices is based on a computer?

2.- Describes the operations that occur in the “op code fetch”:

3.- Draw the diagram to blocks of a generic CPU. Mention the function of each block. Mention the name of the records typically found in each block.

Answer 1

1. 
   Computers and electronic devices use electric signals to accomplish tasks.
   They are using the binary system.
   Computers can work without physical emotions and acts mathematically and logically.
   Computers can be updated with the latest evolving technologies.
   A computer can do multitasks
   Computers are very accurate and speedy.
   The computer can work continuously for hours without getting tired like humans and won't get lazy in doing things.
   
   The above mentioned are some of the advantages of using a computer. Electronic devices are mainly used for repeated tasks, so computers are used. Computers are preferred because humans will definitely get tired and lazy while doing the same tasks again and again and also for performing huge mathematical calculations and logical decisions. So the control of electronic devices is always based on computers.
   
2. 
   OPCODE FETCH
   The microprocessor requires instructions to perform any particular action. In order to perform these actions, microprocessor utilizes Opcode which is a part of an instruction which provides detail(ie. Which operation µp needs to perform) to microprocessor
   
   
   
   

   Operation:

   During T1 state, the microprocessor uses IO/M(bar), S0, S1 signals are used to instruct the microprocessor to fetch opcode.

   Thus when IO/M(bar)=0, S0=S1= 1, it indicates opcode fetch operation.

   During this operation 8085 transmits a 16-bit address and also uses the ALE signal for address latching.
   At T2 state microprocessor uses read signal and makes data ready from that memory location to read opcode from memory and at the same time program counter increments by 1 and points next instruction to be fetched.
   
   In this state microprocessor also checks the READY input signal, if this pin is at low logic level ie. '0' then microprocessor adds wait state immediately between T2 and T3.
   
   At T3, the microprocessor reads the opcode and store it into an instruction register to decode it further.
   
   During T4 microprocessor performs internal operation like decoding opcode and providing necessary actions.
   
   The opcode is decoded to know whether T5 or T6 states are required if they are not required then µp performs the next operation.
   

3. 
   CPU Block Diagram
   
   
   CPU consists of 3 basic units: Control Unit(CU), Arithmetic Logical Uni(ALU) and Memory Unit(MU).
   Input is given through input devices to the CPU.
   CU controls communication with ALU and MU.
   CU gets instruction from memory.
   CU decides what to do of that instruction and transfer it to the ALU.
   ALU performs various arithmetic operations like addition, subtraction, multiplication, division and logical operation like AND, OR, NOT, NAND, etc. on that instruction.
   Results of ALU are stored in the memory or register for its further operations.
   After completing the instruction, stored results are passed to the output devices.
   To synchronize all these operations CPU uses its own system clock.