John Payson <supercat@MCS.NET> wrote:
> IMHO, the host port as Microchip implements it is still somewhat
> limitted, however, since there is no good way to distinguish commands from
> data without adding more external logic.  Think what you like about the
> 8042's instruction set, but having two read addresses and two write addresses
> from the host's point of view can really improve things a lot.

Agreed.  When I first saw the specs, I thought, "Wow, finally a decent
8041/8042 replacement" (since Intel's never done a decent one since).
Given how ubiquitous the 804x are, you'd think someone at Microchip would
have bothered to actually look at it for ideas as to how to make a *usable*
host port.  :-(   Mitsubishi, who I usually don't credit for being
exceptionally clueful, managed to get that right on their 3745x parts.

I'd really like to see three separate registers for data and commands written
by the host to the PIC, but even a single register for both would be OK if
they'd save a 9th bit like to 804x.

Sigh.  Maybe someday some semi company will accidentally stumble onto the
combination of great engineering *and* low prices.  I haven't yet become
convinced that it's impossible.

Maybe we could convince Microchip to send a few of us very early
(pre-tapeout) engineering specs to look over to try to avoid silly design
flaws and limitations like this.

Cheers,
Eric