[Coco] GIME behavior

[Mark Marlette]

Darren,

I went back and looked at one of my designs real quickly. Working on other things ATM...

Are you sure $ff90 is write only? You got me wondering now....I don't think it is...Can I change my position? :)

My use of tracking GIME bits was because the hardware had to modify some signals. Then I tacked the bits back on for the readback.

Looking at my documentations and I can't find exactly what I am looking for......

But I am not seeing that the GIME is write only in that area.

Bits that are not used of course can be tacked on and used.

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.

Regards,

Mark



----- Original Message -----
From: "Darren A" <mechacoco at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, April 13, 2011 5:28:56 PM
Subject: Re: [Coco] GIME behavior

On 4/13/11, Mark Marlette wrote:
> Darren,
>
> This behavior is correct.
> Remap your status register to your IO space.


That is unfortunate.  With the CoCo's limited IO space, many of those
write-only locations could have been put to some good use.


> Using Altera and Quartus? MaxII series is quite verse.


I opted for the MAX 3000A since it is available in a PLCC package and
has 5 volt tolerant IOs.

Darren

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