8085 Instruction set - Branch Instructions

             The branching instructions alter the normal sequential program either conditionaly or unconditionally.

As formerly seen in my previous posts in this Series, we divided the Series into four parts:

• Arithmetic Instructions
• Logical Instructions
• Data Transfer Instructions
• Branch Instructions and I/O, Stack, Machine Control Group Instructions

UNCONDITIONAL BRANCHING INSRTRUCTIONS:

     JMP :

          This instruction is used to jump from one set of programs to another set

                e.g:   In a 8 bit multiplication program, JN2 LOOP it means that if no zero results in previous arithmetic operation, it will jump to LOOP.

    CALL :

          This instruction is used to call the function.

                e.g:   CALL DIV,CALL SUB etc..

    RET :

          This instruction is used to return to the program after doing some manipulation for a program to succeed.

CONDITIONAL BRANCHING INSTRUCTIONS :

          Here we are going to discuss some instructions which we use with jump instruction.

The instructions are

        NZ Not Zero (Z = 0)

        Z    Zero (Z = 1)

        NC No Carry (C = 0)

        C    Carry (C = 1)

        PO Parity Odd (P = 0)

        PE Parity Even (P = 1)

        P   Plus (S = 0)

        M  Minus (S = 1)

        Jumps Calls Returns

        C CC RC (Carry)

        INC CNC RNC (No Carry)

        JZ CZ RZ (Zero)

        JNZ CNZ RNZ (Not Zero)

        JP CP RP (Plus)

        JM CM RM (Minus)

        JPE CPE RPE (Parity Even)

        JP0 CPO RPO (Parity Odd)

        

        Two other instructions can affect a branch by replacing the contents or the program counter:

        PCHL Move H & L to Program Counter

        RST    Special Restart Instruction Used with Interrupts

Stack I/O, and Machine Control Instructions:

    The following instructions affect the Stack and/or Stack Pointer:

        PUSH  Push Two bytes of Data onto the Stack

        POP     Pop Two Bytes of Data off the Stack

        XTHL Exchange Top of Stack with H & L

        SPHL  Move content of H & L to Stack Pointer

The I/0 instructions are as follows:

        IN     Initiate Input Operation

        OUT Initiate Output Operation

The Machine Control instructions are as follows:

        EI      Enable Interrupt System

        DI     Disable Interrupt System

        HLT Halt

        NOP No Operation

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Digital Voltmeter - Part I

Digital Voltmeter ( DVM ) is an Analog to digital    converter (A/D) with a

digital display

TYPES: (based on the type of ADC used)

          1. Dual Slope Type

          2. Ramp Type

          3. Integrating Type

          4. Successive Approximation Type

DUAL SLOPE INTEGRATING TYPE:

          Principle: Dual slope integrating type digital voltemeter has both +ve and -ve slope during integration there by it averages the errors (or) noise that are present in the environment.

          Operation: The start pulse resets the counter to zero, the flip flop gives zero output and keeps switch Si closed and Sr open by switch driver circuit .The integrator integrates in +v direction when zero crossing just exceeds zero. The gate is open allowing the counter to count the oscillator clock. When counter resets to maximum count for the next clock, the counter resets to zero forcing the flip flop output to '1'. In this case, switch Si is open and Sr is closed. Vr (reference voltage) is negative reference,now integrated by the integrator with negative slope and the voltage crosses zero,the zero crossing detector closes the gate, stopping the counter.

           The counts in the counter is proportional to 't2' ( time for integrating Vr (negative slope) towards zero ) and is in-turn proportional to input voltage.

An Expression for Input Voltage:

          Charging Equation:      Vout = -(1/RC) ∫ [ Vi * dt ]    ( interval 0 to t1)

                                                 Vout = -(1/RC)*Vi*t1

         Discharge Equation:     Vout = (1/RC) ∫ [ -Vr * dt ]   ( interval 0 to t2)

                                                 Vout = (-1/RC)*Vr*t2

         From above equations, we get

                                                Vi*t1 = Vr*t2

                                                    Vi = (t2/t1)*Vr

                                        since,  t1 = n1*T

                                            and t2 = n2*T

                                                    Vi = (n2/n1)*Vr

        Hence, Vi is directly proportional to n2.

               where, 

Vout	Output Voltage
R, C	Resistor and Capacitor in the integrator
Vr	Reference Voltage
T	Total time of integration
t1	Time of integration of input voltage
t2	Time of integration of reference voltage
n1	Maximum number of counts
n2	Final count value

Coming up next:

* Ramp Type DVM

* Integrating Type DVM

* Successive Approximation type DVM

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8085 Data Transfer Instructions

       Here we are going to discuss about data transfer instructions which move data between register or memory locations.

As formerly seen in my previous posts in this Series, we divided the Series into four parts:

• Arithmetic Instructions
• Logical Instructions
• Data Transfer Instructions
• Branch Instructions and I/O, Stack, Machine Control Group Instructions

INSTRUCTIONS:

       MOV :

           This instruction is used to move the data from accumulator or memory to some registers or vice versa.

      e.g: If [A] = 00 and [B] = 20

             after MOV A,B

             [A] = 20 and [B] = 20

      MVI :

          This instruction is used to move the data from accumulator or memory to some registers or vice versa using the immediate data

e.g: after MVI B , 09

       [B] = 09

      LDA:

          This instruction is used to load the accumulator directly from the memory.

e.g: assume [4200] = FE

       after LDA 4200 

       [A] = FE

      STA :

           This instruction is used to store the content of accumulator directly to a memory address

e.g: If [A] = FF

       after STA 4200

       [4200] = FF

      LHLD :

           This instruction is used to load H&L registers directly from memory

e.g: If [4200] = FE and [4201] = 29

       after LHLD 4200

       [H] = 29 and [L] = FE

      SHLD :

           This instruction is used to store the H & L registers directly to memory.

e.g: If [H] = 29 and [L] = FE

       after SHLD 4200

       [4200] = FE and [4201] = 29

          Now we are going to see some data transfer instruction which deals with the register pair. To indicate the register pair we are using a term called ‘X’.

 LXI :

     This instruction is used to load the register pair with the immediate data.

            e.g:  after LXI H 4200

                    [H] = 42 and [L] = 00

 LDAX : 

     This instruction is used to load the accumulator with the data from address in register pair( 16 bit address).

            e.g: If [4432] = 3F and [A] = 00

                   [B]= 44 and [C]=32                      

                   after LDAX B

                   [A] = 3F

 STAX :

      This instructions is used to store the accumulator in address in register pair.

             e.g: If [A] = 32 and [D] = 40 and [E] = 00

                    after STAX D 

                    [4000] = 32.

 XCHG : 

      This instruction is used to exchange the data of H&L register pair with D&E register pair.

             e.g:  If [H] = 00, [L] = 01 and

                        [D] = 15 and [E] = 30

                     after XCHG 

                     [H] = 15 and [L] = 30

                     [D] = 00 and [E] = 01

 XTHL : 

      This instruction is used to exchange the top of stack with H&L.

             e.g: If [H] = 20 and [L] = 18 

                   assume that contents of stack is  

                  after XTHL                          

                  [H] = [01] and [L] = [09] and the contents of satck will be 

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Numerical Methods Using MATLAB - Part 5

Graeffe's Root Squaring Method:
           This is a direct method and it is used to find the roots of a polynomial equation with real coefficients. Let us consider an equation of the form:

                         ax3 + bx^2 + cx + d = 0

To find the solution of the above equation, we fill up the following table:

		m		2^m		n1		n2		n3		n4
Given Equation		0		1		a		b		c		d
						a^2		b^2		c^2		d^2
						0		-2*a*c		-2*b*d		0
First Squaring		1		2		a^2		b^2 - 2*a*c		c^2 - 2*b*d		d^2

              Thus, the table goes on. The number of squaring done depends on the required accuracy of the solution. The roots are calculated by using the final values of n1, n2, n3 and n4 as follows:

                   a1^(2^m)=n2/n1

               a2^(2^m)=n3/n2

               a3^(2^m)=n4/n3

          From the above equations, the roots a1, a2, a3 can be calculated.The MATLAB code for solving a polynomial by the above method is given below:

Source Code: 

    % a function that uses Graeffe's method 

    % to calculate roots of Algebraic equation 

    function GraeffeFunc(co,gcount)

             % variable b contains the size of co

             % co  coeff/: vector

             [a b]=size(co);

  

             % initialize count to zero

             count = 0;

            % loop where elements of co vector are squared

            % step by step for further processing

            while count<gcount

                    for i=1:b

                         % for other coeff.

                         if i~=1 && i~=b

                              co1(i)=(co(i)^2)-(2*co(i-1)*co(i+1));

                              % for 1st and last coeff.

                        else

                              co1(i)=co(i)^2;

                        end

                    end

                    count=count+1;

                    co=co1;

           end

           % end of while

           % Finding the solution by operating on co1 vector values

           for i=2:b

               sol(i-1)=(co1(i)/co1(i-1))^(1/(2^gcount));

           end

          % displaying calculated values

          disp(co1);

          disp(sol);

    end

    % end of program

Coming up next:

       * Solution of Simultaneous Linear Algebraic Equations

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