trouble with 6.25 crystal?

ksam

I'm working on a little project trying to make a small video game. I'm using the game Planetary defense from Michael Park:

http://forums.parallax.com/showthread.php?p=770719

I'm trying out the 6.25 crystal instead of the 5 Mhz one.· I've changed the xinfreq to 6_250_000, but this doesn't work.· It works fine with the other crystal?· Any suggestions?

Rayman

If by "doesn't work", you mean you don't get video out... You may need to tweak the video drivers for the higher clock freq...

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Bill Henning

Hi,

Rayman is right - you have to change _xinfreq not only in your top-level object, but in every object it includes.

Worse, some of the drivers build in hidden assumptions about 5MHz (video drivers are worst at this). Look for lines like:

                        movi    frqa,#(pr / 5) << 3     'set pixel rate                                      
                        movi    ctra,#%00001_101        'enable PLL in ctra (VCO runs at 4x)

See that (pr / 5)?

That assumes 5MHz.

Replace that with

                        movi    frqa,#((pr*1000) / 6250) << 3     'set pixel rate                                      
                        movi    ctra,#%00001_101        'enable PLL in ctra (VCO runs at 4x)

Best,

Bill

ksam said...
I'm working on a little project trying to make a small video game. I'm using the game Planetary defense from Michael Park:[noparse][[/noparse]color=#0000ff]
http://forums.parallax.com/showthread.php?p=770719

I'm trying out the 6.25 crystal instead of the 5 Mhz one. I've changed the xinfreq to 6_250_000, but this doesn't work. It works fine with the other crystal? Any suggestions?
[noparse][[/noparse]/color]

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