I'd be curious as to how you will generate the rising form, but...
Let's say you use a 74HC238 to decode the counter.  A resistor connected=20
to each output that represents the sin of the angle. All resistors tied=20
together and going to the - input of an op-amp.  A feedback resistor=20
around the op-amp (output to - input).  The + input could be switched by=20
bit 4 to go from ground to Vmax.
When the count is 7, the op-amp would put out, say -3V.  On the next=20
count, the 238 would put out 0, the + input of the op-amp would be +3V=20
and the output would be -3V, and start going down as the count goes up. =20
When the count reaches 7 again, the op-amp would put out 0V.  When it=20
rolls over again, the + input returns to 0V, and the op-amp will still=20
output 0V.

Does that make sense?

Kerry


Lachlan Mac Donald wrote:
> Hi! Does  anyone know of a simple way to use an upcounter (not up/down )
> counter to generate a sine wave . No problem generating the rising
> section,but can't think of a simple way to generate the falling
> section.Only needs to be 3 or 4 bit,happy to use diode logic, or switch a
> transistor.I do have the next counter stage output, so can use this to
> toggle etc if required.Any thoughts appreciated,thank you. Lach
>  =20

--=20
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