What are the different flags in 8085?
Answer Posted / annamalai
5 flags overall
Sign flag;if the result is zero it is set otherwise it is reset
Zero flag: it is set to 1 then the result of an arithmetic logic is zero and it is reset the result is zero
Parity flag: the parity is used to indicate the number of 1 in a given site. The bit is said to have even parity if it is of even number of flag and the bit is said to have not parity if the bits arr odd number by one. If the result is even it is set otherwise it is reset
Carry flag: the carry flag is set to 1 if the carry is produce by arithmetic or logic operation and it is reset for no carry
Axillary carry flag; the auxillary flag is set to one if it has one d3 position and passed to d4
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what differences can you state between the hlt and hold states?
I have code and test bench however it is not working porperly. Need help to get it working. module fsm(clock,reset,coin,vend,state,change); \\these are the inputs and the outputs. input clock; input reset; input [2:0]coin; output vend; output [2:0]state; output [2:0]change; \\i need to define the registers as change,coin and vend reg vend; reg [2:0]change; wire [2:0]coin; \\my coins are declared as parameters to make reading better. parameter [2:0]NICKEL=3’b001; parameter [2:0]DIME=3’b010; parameter [2:0]NICKEL_DIME=3’b011; parameter [2:0]DIME_DIME=3’b100; parameter [2:0]QUARTER=3’b101; \\MY STATES ARE ALSO PARAMETERS . I DONT WANT TO MAKE YOU READ \\IN MACHINE LANGUAGE parameter [2:0]IDLE=3’b000; parameter [2:0]FIVE=3’b001; parameter [2:0]TEN=3’b010; parameter [2:0]FIFTEEN=3’b011; parameter [2:0]TWENTY=3’b100; parameter [2:0]TWENTYFIVE=3’b101; \\AS ALWAYS THE STATES ARE DEFINED AS REG reg [2:0]state,next_state; \\MY MACHINE WORKS ON STATE AND COIN always @(state or coin) begin next_state=0; \\VERYFIRST NEXT STATE IS GIVEN ZERO case(state) IDLE: case(coin) \\THIS IS THE IDLE STATE NICKEL: next_state=FIVE; DIME: next_state=TEN; QUARTER: next_state=TWENTYFIVE; default: next_state=IDLE; endcase FIVE: case(coin) \\THIS IS THE SECOND STATE NICKEL: next_state=TEN; DIME: next_state=FIFTEEN; QUARTER: next_state=TWENTYFIVE; //change=NICKEL default: next_state=FIVE; endcase TEN: case(coin) \\THIS IS THE THIRD STATE NICKEL: next_state=FIFTEEN; DIME: next_state=TWENTY; QUARTER: next_state=TWENTYFIVE; //change=DIME default: next_state=TEN; endcase FIFTEEN: case(coin) \\THIS IS THE FOURTH STATE NICKEL: next_state=TWENTY; DIME: next_state=TWENTYFIVE; QUARTER: next_state=TWENTYFIVE; //change==NICKEL_DIME default: next_state=FIFTEEN; endcase TWENTY: case(coin) \\THIS IS THE FIFTH STATE NICKEL: next_state=TWENTYFIVE; DIME: next_state=TWENTYFIVE; //change=NICKEL QUARTER: next_state=TWENTYFIVE; //change==DIME_DIME default: next_state=TWENTY; endcase TWENTYFIVE: next_state=IDLE; \\THE NEXT STATE HERE IS THE RESET default : next_state=IDLE; endcase end always @(clock) begin \\WHENEVER I GIVE A RESET I HAVE TO MAKE THE STATE TO IDLE AND VEND TO 1 if(reset) begin state <= IDLE; vend <= 1’b0; // change <= 3’b000; end \\THE CHANGE ALSO HAS TO BECOME NONE else state <= next_state; case (state) \\HERE WE DECIDE THE NEXT STATE \\ALL THE STATES ARE DEFINED HERE AND THE OUTPUT IS ALSO GIVEN IDLE: begin vend <= 1’b0; change <=3’d0; end FIVE: begin vend <= 1’b0; if (coin==QUARTER) change <=NICKEL; else change <=3’d0; TEN: begin vend <= 1’b0; if (coin==QUARTER) change <=DIME; else change <= 3’d0; FIFTEEN : begin vend <= 1’b0; if (coin==QUARTER) change <=NICKEL_DIME; else change TWENTY : begin vend <= 1’b0; if (coin==DIME) change <=NICKEL; else if (coin==QUARTER) TWENTYFIVE : begin vend <= 1’b1; change <=3’d0; end default: state <= IDLE; endcase end endmodule module test; \\THE INPUT IN THE FSM MODULE ARE REG HERE reg clock,reset; reg [2:0]coin; \\THE OUTPUT IN THE FSM MODULE ARE WIRES HERE wire vend; wire [2:0]state; wire [2:0]change; \\THE PARAMETERS AGAIN FOR THE COIN AND STATE parameter [2:0]IDLE=3’b000; parameter [2:0]FIVE=3’b001; parameter [2:0]TEN=3’b010; parameter [2:0]FIFTEEN=3’b011; parameter [2:0]TWENTY=3’b100; parameter [2:0]TWENTYFIVE=3’b101; parameter [2:0]NICKEL=3’b001; parameter [2:0]DIME=3’b010; parameter [2:0]NICKEL_DIME=3’b011; parameter [2:0]DIME_DIME=3’b100; parameter [2:0]QUARTER=3’b101; \\I MONITOR THE TIME,DRINK,RESET,CLOCK,STATE AND CHANGE FOR CHANGES. initial begin $display("Time\tcoin\tdrink\treset\tclock\tstate\tchange"); $monitor("%g\t%b\t%b\t%b\t%b\t%d\t% d",$time,coin,vend,reset,clock,state,change); \\NEW FEATURE: MY MACHINE HAS THE FACILITY TO DUMP VARIABLES SO THAT \\ I CAN VIEW THEM USING A VCD VIEWER. $dumpvars; $dumpfile("file.vcd"); // Dump output file. \\THIS IS WHERE THE COINS ARE ADDED. clock=0; reset=1; \\FIRST LETS RESET THE MACHINE #2 reset=0; coin=NICKEL; \\CHECK FOR STATE 1 #2 reset=1; coin=2’b00; #2 reset=0; coin=DIME; \\RESET AGAIN AND CHECK FOR STATE 2 #2 reset=1; coin=2’b00; #2 reset=0; \\RESET AGAIN AND CHECK FOR STATE 5 coin=QUARTER; #2 reset=1; coin=2’b00; #2 reset=0; \\RESET AGAIN AND CHECK FOR STATE 5 coin=NICKEL; #2 coin=NICKEL; #2 coin=NICKEL; #2 coin=NICKEL; #2 coin=NICKEL; #2 reset=1; coin=2’b00; #2 reset=0; \\RESET AGAIN AND CHECK FOR STATE 5 AND SO ON coin=NICKEL; #2 coin=DIME; #2 coin=DIME; #2 reset=1; coin=2’b00; #2 reset=0; coin=NICKEL; #2 coin=DIME; #2 coin=QUARTER; #2 reset=1; coin=2’b00; #2 reset=0; coin=NICKEL; #2 coin=NICKEL; #2 coin=NICKEL; #2 coin=DIME; #2 reset=1; coin=2’b00; #2 reset=0; coin=NICKEL; #2 coin=NICKEL; #2 coin=NICKEL; #2 coin=NICKEL; #2 coin=DIME; #2 reset=1; coin=2’b00; #2 reset=0; coin=NICKEL; #2 coin=NICKEL; #2 coin=QUARTER; #2 reset=1; coin=2’b00; #2 reset=0; coin=NICKEL; #2 coin=QUARTER; #2 reset=1; coin=2’b00; #2 $finish; end \\THE CLOCK NEEDS TO TICK EVERY 2 TIME UNIT always #1 clock=~clock; //always @(state) // coin=!coin; initial begin if (reset) coin=2’b00; end \\THIS IS WHERE I INSTANTIATE THE MACHINE fsm inst1(clock,reset,coin,vend,state,change); endmodule
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