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Two cogs trying to do VGA on same pins — Parallax Forums

Two cogs trying to do VGA on same pins

RaymanRayman Posts: 14,646
in Propeller 2
Was looking into what happens if two cogs try to do VGA on the same I/O pins.

It looks like whichever cog does wrpin first owns the DAC outputs...

spin2
spin2
VGA_640_x_480_8bpp_Spin4_TwoCog.spin2
9K

Comments

  • RaymanRayman Posts: 14,646
    Was hoping that maybe two cogs could share control of different parts of the screen or that maybe DAC inputs would get OR'd together.
    But, that doesn't seem to be the case...
  • cgraceycgracey Posts: 14,155
    There is a 4-bit selector field in the smart pin configuration that picks which cog's DAC channels are going to be used by the pin. So, it would be practical for cogs to switch driving the DAC channels on a per-scan-line basis, but not on a per-pixel basis.
  • evanhevanh Posts: 15,916
    Least four bits of that pin's "P" field selects the cog number. And least two bits of the pin number defines which of the four dac channels that pin will map to.

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