Search found 464 matches

by Joe
Sat May 08, 2021 1:40 am
Forum: NES Hardware and Flash Equipment
Topic: A hypothetical MMC3-like mapper without a CPLD
Replies: 4
Views: 376

Re: A hypothetical MMC3-like mapper without a CPLD

This is just for fun. You wouldn't build this thing if you're worried about how much it costs.

Although, you could replace the four 74*670 with eight 74*373 (or 74*573), a couple of 74*139, and... two 74*04, I think? Spend the money you save on cheaper parts to get a bigger board to hold all of them.
by Joe
Fri May 07, 2021 12:49 pm
Forum: NES Hardware and Flash Equipment
Topic: A hypothetical MMC3-like mapper without a CPLD
Replies: 4
Views: 376

A hypothetical MMC3-like mapper without a CPLD

Reading about mapper design had me wondering just what it would take to build something like the MMC3 using only new DIP ICs. Turns out it's pretty easy once you have a GAL16V8 . PRG and CHR bank registers can be handled by a bunch of 74*670s. A single *670 can give you four 8KB PRG banks out of a 1...
by Joe
Sat May 01, 2021 5:37 pm
Forum: Reproduction
Topic: SNES VHDL mappers for CPLD
Replies: 3
Views: 763

Re: SNES VHDL mappers for CPLD

Aren't SNES cartridge mappers pretty simple? If you're using 5V ROMs, you might be able to use a smaller 5V-tolerant programmable logic device, like the ones lidnariq suggested in this post.
by Joe
Thu Apr 29, 2021 8:33 pm
Forum: Newbie Help Center
Topic: Making a cart from scratch...
Replies: 75
Views: 14342

Re: Making a cart from scratch...

Is the AX5202P draining the battery? The wiki claims it's possible. If this is what's causing the problem, you'll see it as unusually high voltage drop across one of the resistors even with the RAM completely removed from the board. (I don't know how to check it without removing the RAM. I also don'...
by Joe
Sat Apr 17, 2021 8:09 pm
Forum: NES Hardware and Flash Equipment
Topic: Hitex HT-767 - interesting famiclone
Replies: 5
Views: 2301

Re: Hitex HT-767 - interesting famiclone

My guess is it was meant to be a 4011 to make a NMI delay circuit for compatibility with NTSC games on a PAL PPU, except they accidentally routed VCC to pin 12 instead of pin 14.
by Joe
Sun Apr 11, 2021 9:43 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

That all sounds awfully familiar.

Have you found any other functions that can be enabled or disabled by writing $412F? (Could there be a similar register in the RF5C66?)
by Joe
Tue Apr 06, 2021 7:30 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

Joe: how on earth did you ever make the connection from $4100/4101/4102 writes to the NMI handler? I found the code for dialing numbers. For pulse dialing in particular, it expects a NMI each time it disconnects or reconnects the line, and it has lookup tables it uses to pick values to write to $41...
by Joe
Sun Apr 04, 2021 6:49 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

For the RF5A18 input signals from the modem module, I was very surprised not to find a signal that reflected whether there is a dial tone or not. The MSM6827L has a call-progress tone detector (bit 1 of DR) that can detect tones between 350Hz and 620Hz. I can't say for sure since I haven't looked t...
by Joe
Fri Apr 02, 2021 8:34 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

tepples wrote:
Fri Apr 02, 2021 8:25 pm
Identity of "Joe" has been confirmed. Try editing now.
Thank you, it looks like I can edit pages now.
by Joe
Fri Apr 02, 2021 8:06 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

Would you mind editing the wiki with your findings? I would like to, but I can't figure out how to get access to edit pages. So [key 0] is not even used in calculating the checksum? Not in command 7C/7D/7E/7F. It does contribute to the CRC-16 calculation in command 12. (And looking again at my note...
by Joe
Fri Apr 02, 2021 1:54 am
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

The CRC-16 employed by commands 7C, 7D, 7E, and 7F has the polynomial 0x8385, initial value 0x35AC, and is "reflected" (calculated LSB-first). It's also calculated backwards starting from the last byte of the packet, so you have to reverse the bytes before a typical CRC-16 calculator will give you c...
by Joe
Sun Mar 28, 2021 11:21 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 160
Views: 113328

Re: Famicom Network System (aka Famicom Modem) Investigations

I don't think those modem commands are Hayes commands, so I'm disassembling the CPU2 ROM to try to figure out what they actually are. The subroutine at $E39D appears to write to the MSM6827 CR1 register, which would make $4121 a shift register that outputs one bit at a time each time EXCLK is toggle...
by Joe
Fri Mar 26, 2021 7:02 pm
Forum: NESemdev
Topic: PPU Blarg tests
Replies: 7
Views: 3716

Re: PPU Blarg tests

OAMDMA ($4014) sets the high byte of the source address. The low byte is always zero. OAMADDR ($2003) sets the destination address. With OAMADDR set to 1, writing 2 to OAMDMA reads 255 bytes from 0x200 to 0x2FE and writes them to OAM 0x01 to 0xFF, then reads one byte from 0x2FF and writes it to OAM ...
by Joe
Fri Mar 26, 2021 4:55 pm
Forum: Newbie Help Center
Topic: Making a cart from scratch...
Replies: 75
Views: 14342

Re: Making a cart from scratch...

Device ID comes up as 20 41 if that helps. M27C4001, M27V401, or M27W401. Careful: M27V401 and M27W401 are 3.3V and require level shifters. You probably shouldn't use these chips. Maybe Joe knows of another database too. I'm pretty sure we're using the same database, except yours is newer (I found ...
by Joe
Thu Mar 25, 2021 11:25 am
Forum: Newbie Help Center
Topic: Making a cart from scratch...
Replies: 75
Views: 14342

Re: Making a cart from scratch...

the_wizard_666 wrote:
Wed Mar 24, 2021 9:25 pm
Cart 1: The Mad Wizard
Are you sure this game uses CHR ROM? The copy I found uses CHR RAM...