Re: Strange 8255 behavior

From: Michał Pleban <*lists_at_michau.name*> Date: Thu, 14 Jun 2018 15:22:56 +0200 Message-ID: <5B226C30.5090708@michau.name> · lists_at_michau.name

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.

Regards,
Michau.