VRC7 to YM2413 confusion.

VRC7 to YM2413 confusion.
by on (#153203)
I'm attempting to make an adapter for my TNX-HFX4 to free up a cartridge slot (it only has 4, not enough room for the 5th [6th expansion being a YMZ294 taking the place of a 5B])
I think I've got everything figured out but when I try this out on the YM2413 socket on the board I get no sound output. I've gotten everything that's straightforward, like power and ground, xtal in/out, all the data lines, but when it comes to the YM's /IC, /WE, and /CS, I'm not sure where to put them on the VRC7. I had a small talk with rainwarrior about this and he suggested (or it seemed like it) tying /WE and /CS to the VRC7's W/R line (pin 4) and this thread suggests tying /IC to M2, however after taking these steps, I either get no sound or garbage. I'd have used that thread for everything, but since nothing more than overly-saturated flash photos were uploaded, that option's out. Can anyone who knows anything help out?
Re: VRC7 to YM2413 confusion.
by on (#153204)
The Lagrange Point PCB has some kind of amplifier on it. Maybe the output from the VRC7 is extremely quiet otherwise?

Anyway, connectivity "ought" to be /CS→/ROMSEL and /WE→R/W. The VRC7 doesn't have anything like an /InitialClear input, so I'd just leave that floating.
Re: VRC7 to YM2413 confusion.
by on (#153205)
Thanks, I'll try that out tomorrow. Hopefully this works and I can get those boards made.

EDIT: I forgot to add. /WE and /CS are tied together on the HFX as well under the socket. Should I just connect W/R and /ROMSEL together since W/R is already connected to /WE and /CS?
Re: VRC7 to YM2413 confusion.
by on (#153208)
To clarify, what IaTM told me was that /CS + /WE were bridged for the YM2143, and since this only allows two states (both 0 or both 1), those two states sounded like a /WE function according to the YM2143's datasheet. From the datasheet: both 0 = data writes either register address/contents depending on A0, and both 1 = high impedence data bus.

I didn't review anything else about the adapter idea, so I don't know about any of the other lines or what the expected behaviour of the TNS is for them.
Re: VRC7 to YM2413 confusion.
by on (#153271)
Alright, so I tried it, but for all I know it could be working 100%. The DIP switch to select between on-board YM2413 and VRC7 isn't doing anything as Lagrange Point still works as a sound source despite the switch being in either position (AFAIK, it shouldn't do this at all). I'm out of ideas at this point because I have no other way to test a YM2413.
Re: VRC7 to YM2413 confusion.
by on (#153303)
I've found a schematic for VRC7, hope this helps.
Re: VRC7 to YM2413 confusion.
by on (#153347)
Thanks, but it doesn't really seem to supply anything that already wasn't figured out (besides showing /IC connected to Vcc which makes sense, considering it resets if it's low), plus it's the other way around. Applesorce is using a LP cartridge to drive a YM2413. Then again, I'm pretty sure I'm hideously dense, so I'll pour over this over the next couple of days, start fresh, and hopefully see where I've screwed up because this seems way too obvious.
Re: VRC7 to YM2413 confusion.
by on (#155567)
Connect your VRC7 like this:

Pins to GND:
3, 24, 28, 29

Pins to VCC:
1, 2, 19, 27, 30, 42

R/W (4) > OPLL /WR

How you connect the clock is critical and depends on how the cart is wired. Perhaps it's best fit a new clock crystal specific for the VRC7 and not use the clock from the board. But if you must:

X2 (17) is equivalent to the XIN OPLL pin.
X1 (18) is equivalent to XOUT OPLL pin.

If they're driving the YM2413 from a single clock signal just connect pin 17 of the VRC7 to pin 8 of the OPLL socket. If they're using the oscillator driver from the OPLL you need to connect pin 18 to pin 9 of the OPLL socket. But long wires might cause the oscillator to not work correctly. So you can make it oscillate by mouting a 3.57Mhz oscillator on the VRC7 like this:

gnd ----||--x--|3.57|--x--||----gnd

3.57 is a 3.579545Mhz quartz oscillator, the two capacitors are 22pf "x" is the spot where you connect pins 17 and 18 of the VRC chip respectively.

Respect the rest of the wiring diagram on the Japanese drawing as it's correct.

If this is done correctly you will have sound being output at VRC7 pin 43. Make sure to use a capacitor and have a resistor (2k2 to 4k7) to GND to drain some current otherwise there won't be any sound.