18-01
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/**********************************************************************/ /*Super Off Road U75 */ /*5-bit counter increments every clock cycle */ /*Direction bit is registered on clock edge based on quadrature input */ /*Output is enabled when selected by decoded input signals */ /**********************************************************************/ /** Inputs **/ PIN 1 = CLK; /*one quadrature input used as clock*/ PIN 2 = QUAD; /*other quadrature input used for direction*/ PIN 7 = !OPT; /*optical select*/ PIN 8 = ZA0; /*address*/ PIN 9 = ZA1; PIN 11 = !OE; /** Outputs **/ PIN 12 = !OE_CTL; /*fed back to output enable pin*/ PIN 13 = DIR; /*direction output*/ PIN 14 = CNT4; /*counter output*/ PIN 15 = CNT3; PIN 16 = CNT2; PIN 17 = CNT1; PIN 18 = CNT0; /** Logic Equations **/ /*U75 decodes address 0*/ OE_CTL = OPT & !ZA1 & !ZA0; /*counter and direction updated on clock edge and controlled by output enable*/ DIR.d = !QUAD; CNT0.d = !CNT0; CNT1.d = CNT1 $ CNT0; CNT2.d = CNT2 $ (CNT1 & CNT0); CNT3.d = CNT3 $ (CNT2 & CNT1 & CNT0); CNT4.d = CNT4 $ (CNT3 & CNT2 & CNT1 & CNT0);