Figuring out how the Sega DS-16 interfaces with the Genesis.

I won't be able to get any better quality pictures than what you have now. But I can take the Eagle files you sent me and finish the trace outs up. I'm thinking that at this point our focus on this should be on cart slot interface since the pins interfaced through the expansion port are the same from the cart slot. Simplify the design. Of course that will have to be done after the system is completely traced out in a schematic. Still working on my cables to try it out through the cart slot only. I'm pretty sure it will work.

I'll also open up my Evedrive sometime and see what pins are hooked on it. Not sure what revision I have. I do know that !VCLK is not completely necessary as the Everdrive is capable of generating its own signal. Model 3 Megadrive systems don't have the !VCLK signal and it was made with that in mind. Only benefit of using the signal from the console instead of internal generation is slightly faster SD reads/ writes. That's why the Everdrive options menu has a "Genny 3 mode" option. Still, would be nice to hook it up if it isn't.

I'll have to go over the pins of the Everdrive, Sonic 3, Sonic & Knuckles, and the DS-16 sometime to see what's hooked and what isn't. Make a comparison sheet to see what signals are missing that we'll need. Man do I have a plate load in front of me now...

 

any news from this?

 

Sorry. Life got in the way and I kind of dropped it. I need to get back to tracing the connections out on the PCB. If I can do that then it will go a long ways to making a clone. Also need to finish the adapter I started that will allow the system to be hooked to the cart slot only. I'm confident it will function since the expansion port and cart slot share the same signals with the cart slot having a few more.

 

do you believe sega mega-tech is same? i have mega-tech and maybe i can help.

 

Megatech is a whole 'nother animal. Sure it's based on the Megadrive hardware but it's pretty much one on steroids. Megatech has an 8 slot jukebox sure but it also has a second system for the game instructions and such that is hooked to a second screen.

I don't think it will help here but you are free to document it's operation. Maybe something useful can be found.

 

Today i tried to compare megatech cart slot pinout with my model1 megadrive and found some info. I dont know if they are useful but i will continue my research. Maybe i can find some undocumented pinouts of megatech cart slot B side, like B12, B13, B15, B19, B21, or maybe what are B27, B28, B29, and B31 are used for. Here are the results.

B27 of megadrive connected to ic 315-5309 pin 57
B27 of megatech connected to ic70 74f138f pin 15
B28 of megadrive connected to mc68000 pin 1
B28 of megatech connected to ic52 74hc244c pin 9
B29 of megadrive connected to mc68000 pin 2
B29 of megadrive connected to ic52 74hc244c pin 7
B31 of megadrive connected to mc68000 pin 49
B31 of megadrive connected to ic52 74hc244c pin 5

how does the 74hc244 work? as i found on datasheet B16, B31, B29 and B28 are connected to bus outputs and B2, B18, B20 and B17 are connected to bus inputs.

 

http://www.nxp.com/documents/data_sheet/74HC_HCT244.pdf

The 74HC244; 74HCT244 is an 8-bit buffer/line driver with 3-state outputs. The device can be used as two 4-bit buffers or one 8-bit buffer. The device features two output enables (1OE and 2OE), each controlling four of the 3-state outputs. A HIGH on nOE causes the outputs to assume a high-impedance OFF-state. Inputs include clamp diodes that enable the use of current limiting resistors to interface inputs to voltages in excess of VCC.

Looks like it might just be a signal buffer.

 

im still very ignorant about how this hc buffers work. so i assume there is no useful info here.

 

I don't think the Mega Tech is related to the DS-16 tbh.
The DS-16 is just a glorified cart slot switcher, like sonicdude said.

(I might be making a MD to MT adapter very soon though, as somebody has sent me their MT board to repair.)

The pinouts from Nipedley for the Mega Tech are on the other thread.

Just as a quick exercise, let's look at the pinouts erhanpurple posted.
It's interesting to me to document this stuff.

"B27 on the MT comes from 74F138, pin 15"...

According to Nipedley's pinouts, this is the main /CE (/Chip Enable) signal on the cart slot (the / symbol before the signal name means it's an Active-LOW signal).

It makes perfect sense to come from a 74F138. This is a VERY common address decoder chip.
Only one of the '138 chip's outputs will go Low depending on it's inputs.

This is the main /Enable line for the cart. When this is Low, the cart is enabled, and will output data as long as the /OE (/Output Enable) line is also Low.
There may be more than one chip on the cart (like the MT "Menu" ROM), so there may be more than one /OE pin.

Yep, a 74HC244 is just a simple buffer....

But, it has two /Output Enable input on pins 1 and 19.
These control whether the main inputs are allowed to be driven onto the output pins.

If the /OE pins are Low, then the main input signals will pass through to the output side.
If the /OE pins are High, then the outputs will be in High-Impedance (High-Z) state.

High-impedance basically means high-resistance. So, when the /OE pins are High, the outputs are essentially disconnected from the inputs.
(This lets more than one device / chip to be connected to the same bus, but only one device can drive signals onto the bus at any one time.)

There are two separate /OE pins on a '244 buffer, so that it can separately switch two 4-bit groups (Nibbles) of signals.
Quite often, you'll see pin 1 and pin 19 joined together on the PCB, so it will switch all 8-bits at once.


OK, I think you might have the "B" and "A" side of the Model 1 Mega Drive swapped...

I found this out before, because most of the pinouts on the Web are shown as looking into the CART, and not the cart SLOT!
So, the "front" and "back" row of the cart Slot pinouts are swapped.

I always put the "A" side on the right of my pinouts (ie. looking into the cart SLOT).

On the Model 1, B28 / B29 / B31 is actually A28 / A29 / A31...

A28 - 68000 pin 1 = D4
A29 - 68000 pin 2 = D3
A31 - 68000 pin 49 = VCC (+5V)

This matches the pinouts I have for the Mega Drive.

I'll be confirming more of the Mega Tech pinouts once the board arrives, and I'll look into the B28-B31 signals very closely.

Most of them are already known, but would be good to independently confirm them...

MT B28 should be the /LWR signal from the 68000. This is used as an enable for Writing (+ Reading?) the LOWER Byte on the bus, often used for the save-game SRAM / Sonic 3.
MT B29 should be the /UWR signal from the 68000. This is used as an enable for Writing (+ Reading?) the UPPER Byte on the bus, often for the save-game SRAM / Sonic 3.

Note: When I say "from the 68000", the above two signals are probably from the main chipset instead, and may only be used as /Write enable signals.

MT B30 I call the /SMS_MODE pin. This is normally high for MD / Genesis carts, but tied to Ground (Low) to switch the console to SMS mode.
I think B30 is the same on the Mega Drive too, and you can see it tied Low on the Master Mega Converter...
http://atariage.com/forums/uploads/post-4828-1169683632.png

I'm looking to add an SMS slot to the MD to MT adapter too.

B30 on the MD is labelled /M3 on the schematics, but I'm sure it must be for enabling SMS mode?


MT B31 I'm pretty sure is the /TIME signal (same as B31 on the MD).
This is another /Enable pin which I believe is used for writing to the save game SRAM in carts like S&K?
AFAIK, the /TIME signal is normally asserted when the CPU accesses


@sonicdude - if you can get higher-res photos of the DS-16 board, I can probably finish the Eagle schematic.

@erhanpurple - any info on these rarer systems is useful, but we will know more soon.
I'll try to get some high-res photos of the MT board, and trace a lot of the signals.


OzOnE.

 

that was nice reading, thanks alot. i also have schematics of converter and original files of nipedley, i only find it difficult to make ssf2 to run, it simply gives you orange screen. as you can see here its using pins 27 and 28 or 31 i believe that's the cause or mt itself can not handle 40mbit cart. its really better to start another topic or use the existing, let this topic dedicated to ds16.

 

Sorry to resurrect a year old thread but my ds-16 plays sonic 3 and other games that save like light crusader just fine. I bought my ds-16 nos.