module SN74190 
title 'Synchronous 4-bit up/down counter 
Michael Holley    Data I/O Corp    13 Sep 199'

	sn74190 device 'P22V10';

	Clk,Load,EnaG,Down		pin 1,2,3,4;
	DataA,DataB,DataC,DataD		pin 6,7,8,9;
	QA,QB,QC,QD			pin 16,17,18,19;
	RC,MaxMin			pin 20,21;

	QA,QB,QC,QD			istype 'reg_D,buffer';
	RC,MaxMin			istype 'com';

	Count    = [QD   ,QC   ,QB   ,QA   ];
	Data     = [DataD,DataC,DataB,DataA];

equations

      Count.d = (Count.q + 1) &  Load &  EnaG & !Down & (Count.q  < 9)
	      # (Count.q - 1) &  Load &  EnaG &  Down & (Count.q != 0)
	      # ([1,0,0,1])   &  Load &  EnaG &  Down & (Count.q == 0)
	      # (Count.q)     &  Load & !EnaG
	      #  Data         & !Load;

      Count.c = Clk;

      MaxMin  = (Count.q == 9) & !Down
	      # (Count.q == 0) &  Down;

      RC      = !(MaxMin & !Clk & !EnaG);

test_vectors
       ([Clk,Load,EnaG,Down,Data] -> [Count,MaxMin,RC])
	[.C., 0  ,  0 ,  0 ,  7 ] -> [  7  ,  0   , 1];
	[.C., 1  ,  1 ,  0 ,  0 ] -> [  8  ,  0   , 1];
	[ 0 , 1  ,  1 ,  0 ,  0 ] -> [  8  ,  0   , 1];
	[ 1 , 1  ,  1 ,  0 ,  0 ] -> [  9  ,  1   , 1];
	[ 0 , 1  ,  1 ,  0 ,  0 ] -> [  9  ,  1   , 1];
	[.C., 1  ,  1 ,  0 ,  0 ] -> [  0  ,  0   , 1];
	[.C., 1  ,  1 ,  0 ,  0 ] -> [  1  ,  0   , 1];
	[.C., 1  ,  1 ,  0 ,  0 ] -> [  2  ,  0   , 1];
	[.C., 1  ,  0 ,  0 ,  0 ] -> [  2  ,  0   , 1];
	[.C., 1  ,  1 ,  0 ,  0 ] -> [  3  ,  0   , 1];
	[.C., 1  ,  1 ,  0 ,  0 ] -> [  4  ,  0   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  3  ,  0   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  2  ,  0   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  1  ,  0   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  0  ,  1   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  9  ,  0   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  8  ,  0   , 1];
	[.C., 1  ,  1 ,  1 ,  0 ] -> [  7  ,  0   , 1];
end