Access the sub-cpu code from the main cpu

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Bitybity
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Access the sub-cpu code from the main cpu

Post by Bitybity » Thu Jan 03, 2013 3:17 am

Hello guys.

I have a seen a Sega CD source code today... I'm unable to understand it all because of its mess, but, I think, sometimes it reads and writes data directly from the Sub-CPU.

Is it possible to access this code from the main cpu? If yes, at which address?

Chilly Willy
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Post by Chilly Willy » Thu Jan 03, 2013 5:43 pm

The main cpu can read the word ram at 0x200000 if it has been switched over to the main side. The main cpu can read the program ram at 0x020000 as four banks of 128KB, but needs to halt the sub cpu before reading/writing the ram. You'll find all of that in the Mega CD Software Development Manual.

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