Adding address line to cx4 board (32mb romhack)

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Revenant
Posts: 440
Joined: Sat Apr 25, 2015 1:47 pm
Location: FL

Re: Emulating A21 on 1DC0N or 2DC0N cx4 pcb (32mb romhack)

Post by Revenant » Fri Jan 26, 2018 9:15 am

lidnariq wrote:I think the bizarre HiROM layout is only a weird thing you need to emulate if you want to call the pins on the CX4 always the same thing regardless of how the mapping pin is strapped.

The same output pins always relay SNESA0-A14 and SNESA16-A19; the only difference is how those outputs are connected to the ROM's high address lines. The out-of-order-ness shown in qwertymodo's pinout (13 14 20 15 16) insinuates to me that the naïve map was intended to be HiROM and they did the simplest useful thing for LoROM compatibility.
Yeah, I didn't really intend to emulate it any differently than "normal" HiROM mapping, aside from the bank/ROM switching capability.

lidnariq
Posts: 8778
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Location: Seattle

Re: Emulating A21 on 1DC0N or 2DC0N cx4 pcb (32mb romhack)

Post by lidnariq » Fri Jan 26, 2018 12:04 pm

mightydidz wrote:Is the issue with the romhack or my build?
Your build
First I used a FPZ rom hack that I splitted into 2x16mb
2xam29f016b eeprom and retrostage fx adapter
correct
the eeprom /ce lines are connected to a 139 decoder.
Decoder enabler is vss and inputs are A21 (cx4 pin15) ans vss
Last I connected both eeprom A20 directly to the cx4 RA20 (pin34).
Incorrect.

The CX4 in LoROM mode already relays data from the ROMs through the CX4 when /ROMSEL is low and A22 is low. (That's a 2 MiB region: A0 through A14 and A16 through A21 makes 21 address lines)

The remaining 2 MiB need to be directly connected to the data bus when /ROMSEL is low and A22 is high. It's still LoROM map, so you still need to ignore SNESA15.

mightydidz
Posts: 18
Joined: Wed Jan 24, 2018 12:04 pm

Re: Emulating A21 on 1DC0N or 2DC0N cx4 pcb (32mb romhack)

Post by mightydidz » Fri Jan 26, 2018 1:21 pm

Pardon my ignorance but how can I do that?

Changing my decoder input#1 I got different result

First I connected it to cart edge pin 46 (A21) and I got Interface, Register and Rom errors
Then I connected it to cart edge pin 47 (A22) and only got Register and Rom error.
I was able to boot the game a bit further, past the capcom logo. I got like 3 seconds of the intro scene, full music the the graphics frooze
Finally I connected the decoder input #1 to cart edge pin 48 (A23). Didnt get any error at startup but same thing, cant get to the title screen, still freeze during the intro scene.

Here is another build, a cleaner one so you may better understand how I'm testing it
Image

How to I connect the remaining 2mb directly to the databus?
aka: the second eeprom?
I'm using a 139 decoder to control /ce lines of both eeprom, do I need to wire it differently?

Cant wait to get it working.
Thank you guys for the support

zzattack
Posts: 14
Joined: Wed Oct 21, 2015 4:26 pm

Re: Adding address line to cx4 board (32mb romhack)

Post by zzattack » Mon Jun 18, 2018 2:55 pm

Sorry I didn't see the thread before. It got linked from here where I just posted what I did somewhere in 2016 to achieve what you're looking for. Funny to see how we pretty much went about it the same way.

megamanretro
Posts: 8
Joined: Sat May 05, 2018 9:00 am

Re: Emulating A21 on 1DC0N or 2DC0N cx4 pcb (32mb romhack)

Post by megamanretro » Sat Jul 14, 2018 8:33 pm

mightydidz wrote:Here is some update.
I've been able to have the rom to boot on the cartridge in lorom mode.
But when it load it shows interface register, immmediate register and immediate rom error.
When I try to lunch the game, the capcom logo and intro music starts.. then nothing... I get black screen, then a purple screen .

Here is how I wired my stuff.
First I used a FPZ rom hack that I splitted into 2x16mb
2xam29f016b eeprom and retrostage fx adapter
the eeprom /ce lines are connected to a 139 decoder.
Decoder enabler is vss and inputs are A21 (cx4 pin15) ans vss
Last I connected both eeprom A20 directly to the cx4 RA20 (pin34).

Here is a picture of my working board
Sorry about the fuzzy wiring, its kind of a test board, so I needed to have quick access to /oe, /cs, vss and vcc
Image
Image

Is the issue with the romhack or my build?
I think we are really close to it, a bit of help would be appreciated
Hi man, i've just pass this same issue with a megaman x2+x3 multicart on a rockman x2 donor. i just change the oscilator cristal rmx2 uses a 20mhz a change do 21,4 mhz and worked. i don't know why, but worked.

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