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Re: [MiNT] lp driver patch for the Firebee to extend the parallel port strobe duration

Hi Markus,

Why can't this problem be entirely fixed within the FPGA and not resort
to these additional requirements ?


On 03/10/15 21:35, markus@mubf.de wrote:
> Hi all,
> please find attached a patch to MiNT's lp driver.
> It fixes the problem that with the Firebee's Coldfire processor, the
> parallel port strobe signal is not kept active long enough to be
> recognised by most printers. The original delay was two NOP's between
> toggling the PSG ports which is much too small for the Firebee. I have
> replaced this (only if __mcoldfire__ is defined) with a simple wait
> loop around a nop.
> Loop count has been adjusted to meet the minimum requirement of 750 ns
> for strobe activation according to IEEE 1284.
> This is not entirely clean (if we'll ever have another machine with
> different clock speed, it may fail again), but since the Firebee is
> the only known Coldfire machine with a PSG chip, I'd consider it good
> enough for now.
> Note that this alone is not sufficient to make the Firebee print,
> you'll need a (hopefully soon to be released) FPGA fix as well. It
> also won't work (for yet unknown reasons) with MiNT running on top of
> FireTOS.
> But it will make (with the FPGA fix) MiNT + EmuTOS print on the
> parallel port which I definitively consider an improvement.
> Commit text:
> lp driver patch to extend the parallel port strobe duration on the
> Firebee
> Contributed by Markus Fröschle
> Cheers,
> Markus