module GreyCode;
title 'Greycode Counter using State Machine syntax
Wendey Mueller - April 23, 1993'
 
GreyCode device 'P750';

CLK,HOLD     pin 1,2;
C3,C2,C1,C0  pin 23,22,21,20 istype 'reg_d,buffer';

C,K,X,Z,U,D,H,L = .C.,.K.,.X.,.Z.,.U.,.D.,1,0;

GCODE = [C3,C2,C1,C0]; "counter bits

"define states to generate greycode counter

S0  = [0,0,0,0];
S1  = [0,0,0,1];
S2  = [0,0,1,1];
S3  = [0,0,1,0];
S4  = [0,1,1,0];
S5  = [0,1,1,1];
S6  = [0,1,0,1];
S7  = [0,1,0,0];
S8  = [1,1,0,0];
S9  = [1,1,0,1];
S10 = [1,1,1,1];
S11 = [1,1,1,0];
S12 = [1,0,1,0];
S13 = [1,0,1,1];
S14 = [1,0,0,1];
S15 = [1,0,0,0];

EQUATIONS

GCODE.CK = CLK;

STATE_DIAGRAM GCODE

STATE S0:
   IF HOLD THEN S0 ELSE S1;
STATE S1:
   IF HOLD THEN S1 ELSE S2;
STATE S2:
   IF HOLD THEN S2 ELSE S3;
STATE S3:
   IF HOLD THEN S3 ELSE S4;
STATE S4:
   IF HOLD THEN S4 ELSE S5;
STATE S5:
   IF HOLD THEN S5 ELSE S6;
STATE S6:
   IF HOLD THEN S6 ELSE S7;
STATE S7:
   IF HOLD THEN S7 ELSE S8;
STATE S8:
   IF HOLD THEN S8 ELSE S9;
STATE S9:
   IF HOLD THEN S9 ELSE S10;
STATE S10:
   IF HOLD THEN S10 ELSE S11;
STATE S11:
   IF HOLD THEN S11 ELSE S12;
STATE S12:
   IF HOLD THEN S12 ELSE S13;
STATE S13:
   IF HOLD THEN S13 ELSE S14;
STATE S14:
   IF HOLD THEN S14 ELSE S15;
STATE S15:
   IF HOLD THEN S15 ELSE S0;

@IF (1) {
TEST_VECTORS (
[CLK] -> [C3,C2,C1,C0])
[ 0 ] -> [0, 0, 0, 0 ];
[ C ] -> [0, 0, 0, 1 ];
[ C ] -> [0, 0, 1, 1 ];
[ C ] -> [0, 0, 1, 0 ];
[ C ] -> [0, 1, 1, 0 ];
[ C ] -> [0, 1, 1, 1 ];
[ C ] -> [0, 1, 0, 1 ];
[ C ] -> [0, 1, 0, 0 ];
[ C ] -> [1, 1, 0, 0 ];
[ C ] -> [1, 1, 0, 1 ];
[ C ] -> [1, 1, 1, 1 ];
[ C ] -> [1, 1, 1, 0 ];
[ C ] -> [1, 0, 1, 0 ];
[ C ] -> [1, 0, 1, 1 ];
[ C ] -> [1, 0, 0, 1 ];
[ C ] -> [1, 0, 0, 0 ];
}

END