Re: [stella] What's the purpose of address $29E?

Subject: Re: [stella] What's the purpose of address $29E?
From: "Eric Ball" <ericball@xxxxxxxxxxxx>
Date: Thu, 2 Dec 2004 19:58:57 -0500
> What is $29E used for?

> Could these be accessing the NUSIZx registers?
> BTW, thanks Eckhard for answering my question about the $288 address. I
> looked at Jawbreaker again and yes this is the same as SWCHA. How does
> that work? Am I missing something? These addresses don't show in any
> documentation I have.

The TIA and RIOT don't completely decode the 6507 addressing lines so there
are "shadows" throughout the $0000-$0FFF address range.

The TIA !CS0 and !CS3 are connected to A12 and A7, and it fully decodes
A0-5.  So the TIA is mapped to address %0xxxx0x??????  The RIOT CS1, !CS2
and !RS (RAM select) are connected to A7, A12 and A9 respectively and it
fully decodes A0-6.  So the RIOT is mapped to addresses %0xxRx1???????

$29E = %0001010011110 since A7 ($080) is high, it's a RIOT address.  Since
A9 ($200) is high, it's a RIOT register address.  RIOT register $1E is
(according to the same as
TIM8T except it enables the interrupt from timer to !IRQ.

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