[Coco] GIME behavior

[Mark Marlette]

Darren,

I am going to disagree with you and clearly change my original position..

Here is a snipet of code from one of our products, not released and this works.....

         lda   $FF90	   ; get CoCo 3 INT0 register
         ldb   MMUReg      ; and MMU bank register
         pshs  d           ; save for later

To read these registers, I believe you have to be in the correct mode.

Regards,

Mark
Cloud-9

----- Original Message -----
From: "Darren A" <mechacoco at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, April 13, 2011 6:34:23 PM
Subject: Re: [Coco] GIME behavior

On 4/13/11, Mark Marlette  wrote:
> Darren,
> Are you sure $ff90 is write only? You got me wondering now....I don't think
> it is...Can I change my position? :)
>
> A peek of $ff90 should reveal data.....Ok, just tore down my test setup in
> the lab and did a quick peek at ECB powerup.
>
> $ff90 = $7e at powerup. That looks correct per the memory map in the service
> manual.
>

---

Yes, I'm pretty certain that $FF90 is write-only.  Using PEEK on a
CoCo 3 will return $7E for any IO address that doesn't produce data
(unless the address is below $FF7F and you have an MPI attached).

Darren

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