Re: Mockingboard Schematic in GIF form

[Hans Otten <nobody@yahoo.com>]

"a" <a@aol.com> wrote:

>Bill and Michael,
>this is a great help.  However, I'm confused over the part of the
>schematic that I'm most interested.
>
I have used in the past the following circuit to make a PHI2 signal out of PHI1,
with a RC circuit and a schmittrigger (which also adds to the delay) delevering
the wanted delay and inverting.

                                         74LS14 
PHI 1  --- 270 ohm --------------|> --------- PHI2 of 6522
                                  |
                                 = 82 pf
                                  |
                                GND

This works because:
- PHI2 is the inverse of PHI1
- PHI2 is shifted  about 15-75 ns to PHI1

Comparing the real PHI2 with the generated PHI2 with an oscilloscope showed me
it was close enough.  
Hans, http://www.hansotten.com