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There is a switch that is engaged when the disk is set. If it's ejected then you just unset the disk and the BIOS will throw an error. That much was clear -- thanks for the reply anyway --, but I am wondering about the physical function of the drive. Does the motor still spin if signalled to do so,...

Here is the source code of my newer version. It also includes the audio synthesizer and the disk image parser. Because of some internal changes in the emulator it is no longer so self-contained unfortunately.

http://pastebin.ca/2128362

But since the 6502 ingores the CRC, what's the point to even have the CRC stored on the disc ? Just having it stored on the disc (and ignored by the CPU) won't detect transmission errors. Or is there something I missed ? The RAM adapter will calculate and verify the CRC. (If $4025 bit 4 is set at t...

iirc emulating the FDS correctly results in non-working games because the game dumps themselves are incorrect (missing GAP sections and some other crucial items). Emulators either have to employ hacks or attempt to reconstruct the missing sections in order for it to be operable. Allright, thanks. I...

Last night I struggled implementing FDS support in my emulator. I eventually got it working (as in it loads games successfully), but I am not happy with my implementation.* This is my current implementation. (Sound emulation parts are omitted for brevity.) Though it works, search for instances of &q...

Depending on particular values in the RAM for functionality is bad, I agree, but how about using the RAM contents to seed the random generator? Is reading the RAM after poweron a bad idea on electronic basis, or is it just a bad idea because of programming practices basis? In the former case, trying...

If you must not read the RAM upon powerup/reset, how are you supposed to detect that the reset button was pressed? Some games do that.

Having the source code should help a bit. EDIT: My script for plp was: [1450] => tick(); t = Pop(); [1740] => P.raw = t & ~0x30; [1299] => tick(); I.e. one cycle for opcode fetch (implied) One extra cycle One cycle for RAM fetch One extra cycle For a total of 4 ticks. Are you sure your NMI timin...

Human beings appreciate redundance and choice. That you can navigate half a screen right and two rows up by going first right and then up, or by going first up and then right, or maybe go left and wrap through the screen edge and then up, or vice versa, or maybe you'll rather wrap vertically, or may...

It should also greatly simplify the code required to make this work. Each byte of data will correspond to exactly 2 symbols. Not to mention the lack of entry screen. With 4 symbols, you can convey 2 bits of information: 00, 01, 10, 11. You need four of those for eight bits of data, i.e. a byte. To ...

One more thing: In my opinion, while the passwords should be readable, they should not have obvious patterns. If you record a password, and get e.g. "0000a0001", and you then change one thing in the game and get another password, which is "0000b0001", it all too easily tempts the...

For the record, here's the Japanese Maniac Mansion password entry screen: http://bisqwit.iki.fi/cv2fin/comparative_screenshots/maniacj.png 66 symbols, filled into (6+8+7)*5-1 = 104 slots, as indicated by Lidnariq earlier. That's almost twice the amount of information carried in an SMS, considering t...

Have you considered leaving out the encryption/checksum? Considering how easy it is to defeat any nes password system with the tools we have available these days. It may not be worth the effort and rom space to bother. In my opinion, while it is encouraging for hacker spirit for the password system...

Here are samples of some other password generators. http://bisqwit.iki.fi/cv2fin/comparative_screenshots/metroid.png Metroid passwords are 24 characters long, with an alphabet of 64 letters, for a total of 144 bits of data. That 144 bits includes a 8-bit checksum that is calculated from the other bi...

Case study: Simon's quest (USA) has a password of length of 16 characters, with a 32-character alphabet. The password encodes 16 bits of item on/off flags, 8 bits of item counters, 8 bits of day counter, 2 bits of crystal level, 3 bits of weapon level, 3 bits of player level, 8 bits of crypting spec...