Debugging suggestions needed (Zelda)

Discuss emulation of the Nintendo Entertainment System and Famicom.

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nes

Debugging suggestions needed (Zelda)

Post by nes »

My nes emulator works fairly well, but I don't know how to find the obscure bugs in the 6502 core.

My emulator passes all test in both nestress and nestest, but there is still a cpu bug.

The bug is in the legend of zelda. When I press start to view the item screen, the screen scrolls down from the top, but immediatly after the "game over" screen is displayed asking whether I want to continue, save, or retry.

I could write debug logs but I don't know how to sync my log up with the one genereated by the FCE tracer.
Guest

Post by Guest »

Are you allowing input on controller #2 ($4017)? Zelda is supposed to show the game over screen if Up and A are pressed simultaneously on controller #2 while the item screen is visible.

If you're not implementing controller #2, be sure $4017 does not return a 1 in bit zero, and the game should work.
nes

Post by nes »

That was it. Thanks
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