MD II overclock variable

[dadou]

Hi i tried to do my new mod for my MD II it's a overclock variable


i used the LTC1799 chip for doing the mod,i got a overclock of 8.33 Mhz~10Mhz here's the schematic:



you can see the mod in action here: P1040212.MOV

but i need help to finish the mod:

i can't switch between normal mode and overclock mode without the halt mode (pin 17 on the processor) and i don't want to use a second switch
i want also to put a bi-color led for showing the mod
all of this with only one switch

how can i do this?

thx for your help

[bigsanta]

Maybe a 74hc157? It works as a quad spdt switch ,with your single 1 spdt switch operating them all at once.Should be easy enough to connect up whatever else you need to it?

[dadou]

hi thx you for your answer but i didn't understand how the 74HC1757 work 

i need to do this:

when i select normal mode nothing happen only a led need to switch on because it's the default mode
when i switch to overclock mode i need to halt the processor for a little time the time that the output of the ltc1799 will be connected and after this remove the halt mode and switch on a led

i hope you will understand me 

if not i will provide a diagrams of the step

[dadou]

i did it!! with the help of Heero_91 from the forum of Obsolète-Tears

The circuit should work because i did a simulation on my computer with the program Multisim 11.0 if someone know it

here's the schematic:



The circuit work like this:

when i'm in normal mode and i switch to overclock mode i get a negative pulse of 0.5µs on the pin 17 of the processor (Halt pin) from the first Timer, when i switch back to the normal mode i will get a negative pulse of 0.5µs on the pin 17 of the processor (Halt pin) from the second Timer.
The Nor gate is here to let one of the output of the Timers.

Features:

-Overclock variable from 8.33Mhz to 10Mhz (with a potentiometer)
-Halt of the 68000 processor when you switch between the mode (0.5µs)
-Led Bi-color for showing the status

All of of this with only one switch!!

Note: you can use a NE556 instead the two NE555

hope you will like this mod