Subject: [stella] 3F 74LS173 ... how? From: Adam Wozniak <adam@xxxxxxxxxxxxxxxx> Date: Wed, 1 Jun 2005 09:12:09 -0400 |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Thought I'd post some notes re: 3F and the 74LS173, since it took me a little headscratching to figure out. datasheet at http://sipi.usc.edu/~weber/ee459/datasheets/74LS173.pdf 74LS173 "M" is tied to ground. 74LS173 "N" is tied to A11. 74LS173 "/G1" is tied to A7. 74LS173 "/G1" is tied to A6. 74LS173 "CLK" is tied to enable/A12. When A7 and A6 are low, followed by a high transition on A12, the 74LS173 loads its flip-flops. This means we can't access the TIA at 00-3F, we must use 40-7F. This also means we can't switch banks from code running in RAM. It seems that, with one 74LS173, we could access 16 2K segments for a total of 32K. With two 74LS173 in parallel, we could access 256 2K segments for 512K. - -- adam@xxxxxxxxxxxxxxxx http://cuddlepuddle.org/~adam KG6GZR http://cuddlepuddle.org/~adam/resume.html -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFCnbQDyvXf5Z0z5zERAvT6AKCU9PqRobHZshEqBQYMVdeSdzdUyACgohrZ 3aBNs0hB0FyPdv2GntplCGo= =cWjj -----END PGP SIGNATURE----- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [stella] sim65?, B. Watson | Thread | Re: [stella] 6502 superoptimizer up, B. Watson |
Re: [stella] Games using unofficial, Fred Quimby | Date | Re: [stella] 6502 superoptimizer up, B. Watson |
Month |