DM644x VPBE and DCLK

BMillikan

Other Parts Discussed in Thread: THS8200

I need to drive a VGA video display with a THS8200 chip and I'm trying to detemine if I need a PLL or if I can use the DCLK in the VPBE of the DaVinci? Can I hook up the VCLK and use it as my variable clock for my VGA resolutions (I need a 40MHz clock for 800x600@60Hz SVGA and 25.175MHz for 640x480@60Hz VGA).

Thanks!

over 16 years ago

0 Juan Gonzales over 16 years ago

TI__Mastermind 37340 points

You can use DCLK to slow down your ENC_CLK ( 27 MHz on our EVM), but not to speed it up to your desired 40 MHz. That said, your internal data rate will not be affected, so in ensense you will be sub-sampling your data if you slow the clock via DCLK registers (useful to interface to some LCDs).

0 BMillikan over 16 years ago in reply to Juan Gonzales

Intellectual 870 points

What about the MUX at the MXI input? It looks like it can be made into a 54MHz clock? Can that be converted into a 40MHz clock rate after that point onto the VCLK pin?

0 epalmer over 16 years ago in reply to BMillikan

Prodigy 80 points

Can the MXI input simply be changed from a 27MHz crystal to a 40MHz crystal at the MXI input?

0 Juan Gonzales over 16 years ago in reply to epalmer

TI__Mastermind 37340 points

MXI input can only be 27 MHz or 36 MHz per data-sheet. Also, please note that these inputs are used to derive other peripheral clocks; therefore changing any of them may affect the performance of other peripherals. If you need to add another crystal, the EXTCLK or PCLK pins are a better choice.

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DM644x VPBE and DCLK