RE: [stella] Questions of a graphic nature

Subject: RE: [stella] Questions of a graphic nature
From: "John Saeger" <john@xxxxxxxxxxx>
Date: Sun, 29 Aug 1999 23:55:05 -0700
> Does anyone have a comprehensive memory map for the VCS?  (including all
> the mirrors of various parts?)  It would be really helpful, especially
> when doing in-cart hardware.

There are so many copies of the TIA registers, RAM and such that it would be
impractical to draw it out as a map.  Hopefully you know what I mean by the
1000 bit, the 200 bit and the 80 bit in hex.  These are the important
addressing bits.

If the 1000 bit is set then it is a ROM (cart) access.  Otherwise it is
either a TIA, RIOT register or RAM access.  The rules to decide which is
accessed are:

If the 200 bit is set and the 80 bit is set then it's a RIOT register
access.

If the 200 bit is not set and the 80 bit is set then it's a RAM access.

If the 200 bit is not set and the 80 bit is not set then it's a TIA access.

As a general rule, it's probably a good idea to only trigger in-cart
hardware if the 1000 bit is set.

John


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