City Figher 4 with ext audio (Mapper 266)

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q5911
Posts: 20
Joined: Fri Mar 19, 2021 2:14 pm

Re: City Figher 4 with ext audio (Mapper 266)

Post by q5911 »

krzysiobal wrote: Mon Apr 12, 2021 2:45 am I will make the cartridge in free time to verify. Honestly I would prefer the AX5202P (MMC3) as this chip is more common and all Street Fighter versions I have encountered so far used it, but that would require modifying the ROM.
Help,I have been working on the verification of this cartridge during this period of time, but I still haven't succeeded. I hope you can help me to describe the logic of (CPU_R_nW, CPU_ROMSEL, CPU_A14, CPU_A13, CPU_A12) and (VRC4_900C). I use some logic chips to realize it.I think that's the problem.
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krzysiobal
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Re: City Figher 4 with ext audio (Mapper 266)

Post by krzysiobal »

q5911 wrote: Thu May 27, 2021 10:19 pm Help,I have been working on the verification of this cartridge during this period of time, but I still haven't succeeded. I hope you can help me to describe the logic of (CPU_R_nW, CPU_ROMSEL, CPU_A14, CPU_A13, CPU_A12) and (VRC4_900C). I use some logic chips to realize it.I think that's the problem.

* Sorry, I was wrong in the reverse engineer: VRC pin 3 should be CPU-A3 and VRC pin 4 should be CPU-A2, not vice versa

* Because VRC-CPU-A13=CPU-A14 and VRC-CPU-A14=CPU-A13 and VRC-PRG-A14 seems to be PRG-ROM-A14 and VRC-PRG-A13 seems to be PRG-ROM-A13, it means that current order of banks in dump does not match the physical way they are ordered in the EPROM. The best fix is to rewire VRC-PRG-A14 to PRG-ROM-A13 and VRC-PRG-A13 to PRG-ROM-A14

* After those two corrections, you should be able to run game with your current wiring and current PAL. However, if you're really sure your VRC does not have $9003, I was able to squeeze almost every logical input inside the PAL (the one that did not fit was CPU_ROMSEL and CPU_RnW - you have to OR-them externally (for example using diode and resistor) and fed into PAL. Use the attached schematic and attached PAL fusemap.

Code: Select all

CPU /ROMSEL -1k--+--- nROMSEL_or_RnW
CPU R/W -----|>--+
The provided PAL can be used to either be completely independent of VRC $9003:
* PAL pin 1 = nROMSEL_or_RnW
* PAL pin 2 = CPU A11
* PAL pin 3 = not connected
* PAL pin 4 = CPU A14
* PAL pin 5 = CPU A13
* PAL pin 6 = CPU A12

Or to use the VRC $9003:
* PAL pin 1 = VRC $9003
* PAL pin 2 = CPU A11
* PAL pin 3 = not connected
* PAL pin 4 = GND
* PAL pin 5 = GND
* PAL pin 6 = VCC
sch.png
I've just make a test cartridge for it (what is wired to PAL pin 1/4/5/6 selected using jumpers) and it works in both ways
20210601_161409.jpg
20210601_161414.jpg
Attachments
proj_eqn+jed+log.zip
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q5911
Posts: 20
Joined: Fri Mar 19, 2021 2:14 pm

Re: City Figher 4 with ext audio (Mapper 266)

Post by q5911 »

After those two corrections, you should be able to run game with your current wiring and current PAL.
yes! It's really working. I even heard the rough PCM sound. It's really grungy. :lol:
Thank you for your contribution!
bg8eqb
Posts: 19
Joined: Mon Nov 11, 2019 7:46 am

Re: City Figher 4 with ext audio (Mapper 266)

Post by bg8eqb »

q5911 wrote: Thu Jun 03, 2021 4:32 am
After those two corrections, you should be able to run game with your current wiring and current PAL.
yes! It's really working. I even heard the rough PCM sound. It's really grungy. :lol:
Thank you for your contribution!
Great, did you fully replicate it? Is there a test video?
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