Subject: Re: [stella] 7800 ROMBlaster Schematic Done From: Kevin Horton <khorton@xxxxxxxxxx> Date: Tue, 25 Jan 2000 01:27:51 -0500 (EST) |
At 18:19 1/24/00 +0100, you wrote: >>This circuit was designed for a 32K ROM, though it should work on 8, 16, and >>32K ROMs. (I also assumed 8000-ffff was cart space. Correct me if I'm wrong >>on this (so I can fix the circuit and code example) > >The cart space is $4000-$FFFF. OK, not a problem >Is $3f a special register for your circuit or are you trying to write >to the 7800 state control register? If it's the later, I think you are >aiming a bit too high. This register can only be accessed through addresses OK, I didn't remember that. been a long time since I've dorked with the 7800 and I was going by memory. Yeah, replace 3F with say, 00. >The correct value for locking in a 7800 game with full MARIA and RAM >support should be %0000 0111. I was going by memory and the schematic again. :-) >> And the vectors will need to be located two places in the ROM- >> one with A12 and A14 both low. (AFFC, AFFD for the reset >> vector.) > >But then the game ROM would have to be at least 32kb, right? Naaah. The only stipulations are: The "blaster" code be in 8000-ffff, where A12 are A14 both low, and A15 is high. Thanks for the input! -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [stella] 7800 ROMBlaster Schema, Eckhard Stolberg | Thread | [stella] using a real 2600, a learn, Rob |
[stella] using a real 2600, a learn, Rob | Date | RE: [stella] 7800 programs -- poten, Kevin Horton |
Month |