Re: Strange 8255 behavior

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Sat, 16 Jun 2018 19:51:40 +0200
Message-ID: <CAESs-_wL-xr5BosbNmXuq-DUFkkByVYKNT2NDw1WsOHrBJ3T=g@mail.gmail.com>
On Sat, Jun 16, 2018 at 1:43 AM, Jim Brain <brain@jbrain.com> wrote:
> On 6/15/2018 9:42 AM, Francesco Messineo wrote:
>>
>> that would be actually only 16 macrocells. One of the examples on
>> WinCupl makes 3 x 8 bit ports with DDR on a 32 macrocells CPLD, so the
>> same macrocell it's been used for the port bit and its DD bit
>> (probably different functions of the same FF).
>> The result doesn't change much I think.
>
> I can't see how that would work.  You need 2 stateful cells per IO pin for
> this use, and MCs only have 1 flop.  Maybe they did a byte wide DDR (1 bit
> for the entire byte of data).  Can you share a link to the specific CUPL
> example so we can see how they implemented it?

you would need to download wincupl then look at the examples. It's bit
by bit DDR. I can send you the cupl source if you don't want to
install wincupl.


F
Received on 2018-06-16 20:02:13

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