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[/] [vtach/] [trunk/] [bcdadd.v] - Blame information for rev 2
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wd5gnr |
`timescale 1us/1ns
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/* Flull blown BCD adder -- takes number + sign bit and returns result in same format
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Note the number is always a positive representation
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so that 1001 is -1
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Also note that BCD and hex are exactly the same except for legal digits
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do 13'h1001 is actually BCD -1 */
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module bcdadd(input [16:0] a, input [12:0] b, output [16:0] z);
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wire [16:0] ain;
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wire [12:0] bin;
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wire [16:0] zout;
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wire [16:0] ztemp;
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// The bcdneg modules return either a positive # or a 9's compliment #
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bcdneg17 aneg(a,ain);
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bcdneg13 bneg(b,bin);
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// Add the converted numbers
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usum adder(ain,bin,zout);
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// the bcdneg module is reversible so if we feed it 9's compliment we get
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// our format back out
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bcdneg17 zneg(zout,ztemp);
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// sometimes you get -0 and we don't want that so filter it here
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assign z=(ztemp==17'h10000)?(17'h00000):ztemp;
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endmodule
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