GARTHWILSON wrote:
backspace119 wrote:
So I just found
this which seems perfect, but it's resistance controlled, and I'm not sure if it can be changed while live yet. Thoughts?
It's the resistance to Vcc. You should be able to have a set of resistors switched in or out by a VIA's (or similar I/O IC) port bits. One end of each resistor goes to that pin on the part you found, and the other end of each resistor goes to a VIA port pin. Put 1's in every relevant bit of the port's output register. Then to connect the resistor, make the data direction bit an output. To disconnect it, make it an input. WDC's 65c22's port pins are truly high-impedance in the input mode, unlike other companies'. This is not an R-2R ladder. Every resistor will have a different value.
Sweet, so then I can probably use this just fine, the rise time on it looks pretty decent too.
The via idea I'm not sure about, it seems like a waste of via pins for clock control, I may try and find another way to switch out resistance on it.
Arlet wrote:
Or use a digital potentiometer. If you get a non-volatile kind, it will remember the setting when the board is powered down.
This is probably what I'll do, the only issue with a non volatile one would be setting a too high clock and not being able to set it back or save myself by just resetting. Also, at power up it needs the slow clock, so if I had a power failure it wouldn't be able to reboot.
Still though, digital pot is probably the way to go, I just wasn't sure if I could change the frequency live.
BigEd wrote:
Some recent ideas in this (long!) thread which might benefit from new dedicated threads:
- continuously-variable clocking of a 6502 system
- porting DOOM to a 6502 system
- Mouser's filtering mixes up surface-mount and through-hole
Good idea, I'll post some more threads about the individual ideas to keep things organized, should I still post them in newbies? Or elsewhere?