Re: Strange 8255 behavior

From: Marko M�kel� <*marko.makela_at_iki.fi*> Date: Fri, 15 Jun 2018 16:45:38 +0300 Message-ID: <20180615134538.GA7310@jyty> · marko.makela_at_iki.fi

Hi,

On Thu, Jun 14, 2018 at 03:22:56PM +0200, Michał Pleban wrote:
>Hello!
>
>Francesco Messineo wrote:
>
>> yes I know how to count macrocells, I just didn't check how many would
>> be needed for a 6526.
>> 128 is quite a lot I would think.
>
>A very crude calculation:
>
>* Two 8-bit ports with direction pins: 2x2x8 = 32
>* One 8-bit serial port = 8 + some unknown overhead
>* Two 16-bit counters with preset = 2x2x16 = 64
>* TOD clock with alarm: 2x28 = 56
>* Interrupt logic = unknown, but I would assume at least 8-16
>
>That is already way over 128.

These functions are fairly independent of each other. Would it be 
feasible to implement the CIA in two CPLDs that would share the address 
and data bus interface?

	Marko