This was posted to the list a couple days ago:
Not quite. ;-) In FE bankswitching A13 is used to identify the
two banks. Since this line isn't brought out of the 6507, the
FE bankswitching logic waits for two consecutive accesses to
this stack. Only JSR/RTS (and BRK/RTI) can do that. At the second
access the high byte of the return address is either pushed onto
or pulled from the stack. This is where the bankswitching logic
finds out which bank need to be mapped in.
-----Original Message-----
From: owner-stella@xxxxxxxxxxx [mailto:owner-stella@xxxxxxxxxxx] On
Behalf Of Mickey Mouse
Sent: Friday, December 13, 2002 9:56 AM
To: stella@xxxxxxxxxxx
Subject: [stella] FE Bankswitching
Can someone help me out with FE Bankswitching? I am
working on a Cart Emulator and I cant figure out how
FE works. The sizes document is wrong according to
the stella emulator code documentation. The code
is written from the processor point of view so it is
easy, just look at address bit 13. But the cart cant
see address 13. The cart has to know when to switch
from the bus (contrary to the code documents), the
bus is all it has.
Any help would be great! My star doesnt shine real
bright, so use little words please. Explain from
carts point of view. Thanks
Vern
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