Re: [cc65] C64 Cartridge clarifications

From: Thomas Giesel <skoe1directbox.com>
Date: 2012-03-07 22:01:39
GAME and EXROM are two control lines at the expansion port. Their
normal state is "high" (about 5V), which is usually called "1" in
documentation.

Cartridges can pull them down to "low" (about 0V, usually called "0") to
change the memory map of the C64, it gives some additional
configurations or different meaning to what software can do with $01.

These lines are low-active. This means that they are called active when
they are 0.

AFAIR there is a mistake or a fuzzy description of
"active/inactive/1/0" in the CRT documentation or even in the CRT
format, so be careful. A normal 16k Cartridge has both lines low.

Read this and the subsequent chapters for details:
http://www.devili.iki.fi/Computers/Commodore/C64/Programmers_Reference/Chapter_5/page_260.html

Hope this helps.

Thomas

Am Tue, 6 Mar 2012 09:17:48 -0800 (PST)
schrieb Joseph Rose <rose.joseph12@yahoo.com>:

> Sorry fo dominating the mailing list, but I have another issue.  I've
> ben looking at the C64 cartridge documentaion and don't understand
> the purpose of the EXROM and GAME line statuses.  Can anybody clarify
> their purposes for me?  Thank you. -------------- Joseph Rose, a.k.a.
> Harry Potter Working magic in the computer community


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Received on Wed Mar 7 22:01:52 2012

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