Module Count116
Title 'Arbitrary length counter with Carry Out
Michael Holley    Data I/O Corp   30 May 1990'

	count116 device 'P16R8';

	Osc,IncAdr,ClrAdr,OE		pin 1,3,2,11;
	!A6,!A5,!A4,!A3,!A2,!A1,!A0	pin 18,17,16,15,14,13,12;
	!CarryA				pin 19;

	" Note that the outputs are active low.

	H,L,Z,X,C	= 1, 0, .Z., .X., .C.;

	CountA	= [A6,A5,A4,A3,A2,A1,A0];

" This counter uses registered look ahead carry to implement an 
" arbitrary length count.
" The D input to the CarryA register will be high at the 115 count.
" On the next clock with IncAdr high the CarryA will be set and
" the count will advance to 116. 
" The counter keep incrementing as long a CarryA is low, so the
" counter will return to 0 on the next clock with IncAdr high.

Equations 

CountA := (CountA.fb + 1) &  IncAdr & ClrAdr & !CarryA.fb
	#  CountA.fb      & !IncAdr & ClrAdr;

CarryA := (CountA.fb == 115) &  IncAdr & ClrAdr
	#  CarryA.fb         & !IncAdr & ClrAdr;

CountA.clk = Osc;
CountA.oe = !OE;

CarryA.clk = Osc;
CarryA.oe = !OE;

test_vectors
       ([Osc,OE,ClrAdr,IncAdr] -> [CarryA,CountA])
 	[ C , 0,  0   ,  1   ] -> [  0   ,   0  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   1  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   2  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   3  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   4  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   5  ];
 	[ C , 0,  1   ,  0   ] -> [  0   ,   5  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   6  ];
 	[ C , 0,  0   ,  1   ] -> [  0   ,   0  ];

@const i=1; @repeat 112 {
	[ C , 0,  1   ,  1   ] -> [  0   , @expr i; ]; @const i=i+1;}

 	[ C , 0,  1   ,  1   ] -> [  0   , 113  ];
 	[ C , 0,  1   ,  1   ] -> [  0   , 114  ];
 	[ C , 0,  1   ,  1   ] -> [  0   , 115  ];
 	[ C , 0,  1   ,  0   ] -> [  0   , 115  ];
 	[ C , 0,  1   ,  1   ] -> [  1   , 116  ];
 	[ C , 0,  1   ,  0   ] -> [  1   , 116  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   0  ];
 	[ C , 0,  1   ,  1   ] -> [  0   ,   1  ];
end