Sega TeraDrive motherboard pics

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Nemesis
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Post by Nemesis » Sun Apr 29, 2012 1:16 pm

Yep, I'm very mindful of that. A lot of this stuff has been sitting in storage for awhile now with no proper backups, and it's been eating away at me to the point that I'm finally doing something about it. I've managed to make full floppy disk images with no bad sectors of all disks, which took a hell of a lot of work, since there were plently of unreadable sectors when the disks first came to me. I learned a lot of tricks for recovering the unrecoverable in this process. Everything I've backed up so far is stored locally and off-site, so it should be covered.

I need to do more still though, I don't have decent drive images for the TeraDrive systems. They're problematic, since the drive interface is an ancient ESDI interface, and the system itself is a 286, which limits my software choices. I've collected some old tools capable of reading raw drive sectors that should run on a 286, just got to give them a try when I have the time to set everything up. If it works, I should be able to copy sector blocks off to floppy disks bit by bit until I get the whole drive image. This will be important, since I have an installed version of the puzzle construction software, but no install disks unfortunately. I've copied those files off manually, but I'd like to get a full drive snapshot of the working install.

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Post by Nemesis » Thu May 24, 2012 12:56 am

TmEE co.(TM) wrote:Yep, that's the manual. I would suggest more people send him a mail and kindly asking to provide better scan, particularly that one page, so the ASIC pins names get all mentioned. Or maybe he could just write them down. We pretty much know all what they are, just not those "mystery pins"
Here you go:
http://nemesis.hacking-cult.org/MegaDri ... nual/7.jpg
http://nemesis.hacking-cult.org/MegaDri ... nual/8.jpg
http://nemesis.hacking-cult.org/MegaDri ... ual/15.jpg
http://nemesis.hacking-cult.org/MegaDri ... ual/20.jpg
http://nemesis.hacking-cult.org/MegaDri ... al/29a.jpg
http://nemesis.hacking-cult.org/MegaDri ... al/29b.jpg
Never say I don't give you anything. :)

I requested the pages that, after a close inspection, seemed the most useful. These pages show the complete pinout for the 315-5487, as well as the pinout for the daughterboard connector, the cartridge port and expansion port, and a high-level block diagram of how the card works as a whole, and the connections between the main sections. I also obtained scans of the circuit diagram for the monitor, since that's what I requested the scans for in the first place, with the scans of other pages being an added bonus. I think my MegaPC monitor has an intermittent fault, so the schematics will help with that, and anyone else who has these monitors and wants to service them. The other pages in the manual seemed to be to be trivial, readable enough, or well known from the existing Mega Drive schematics. Let me know if there are any more pages you think we could benefit from getting better scans of. I didn't want to push my luck and ask for too much up front.

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Post by Nemesis » Thu May 24, 2012 1:11 am

Looking at the 315-5487 pinout, there are a few interesting things. Obviously there's the pins there for a third controller port, but there are also 4 test pins (81, 82, 83, 84), and a few pins from the 315-5364 bus arbiter in the original Mega Drive (SOUND, ZV, VZ, I/O) which were used to communicate with the 315-5309 discrete IO controller, which are no longer required with the single-chip solution given by the 315-5487.

In terms of the VRAM interface, pins 9 and 14 are SE1 and WE1 like I suspected. Pins 17-25 are labelled as RD0-7. Not really sure what that's supposed to stand for. SD0-7 stands for "Seral Data", and connects to the VRAM serial data pins. AD0-7 connects to both the address lines and data lines for the VRAM, making use of the fact that the VDP never needs to assert the address lines at the same time the VRAM is asserting the data lines. AD might stand for "Address/Data"? RD0-7 is probably the same as AD0-7, but for the second RAM bank, but I'm not sure what it's supposed to stand for. It might stand for "RAM Data", suggesting maybe this line is only connected to the data port on the second bank of VRAM, and both banks share address lines from AD0-7? I'll need to take a look at the way the TeraDrive connects its VRAM banks to confirm.

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Post by TmEE co.(TM) » Thu May 24, 2012 10:41 am

Whoa !!! :shock:

SOUND pin seems to disable all sound when tied to GND, at least so I remember.

This pretty much solves all mysteries, and also we now know MD2 ASIC has no digital color bus like MD1 VDP does...

I will take a much closer look when I get home. This seriously made my day :D
Giant "thänk you" to you ^^
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Post by Nemesis » Thu May 24, 2012 10:56 am

I'm glad it's helpful, documents like this are hard to come by. Don't thank me though, thank the guy who runs the site. I'm glad he was willing to share. I'm sure you asking about pages already helped the matter. I hope one day he'll scan the whole manual again like this.
SOUND pin seems to disable all sound when tied to GND, at least so I remember.
Just realized I didn't finish saying what I meant to say about this in my earlier post. The SOUND line from the original bus arbiter was the CE line running to the YM2612. If tying that pin to ground on the 315-5487 affects sound, the pin must be directly tied to the internal CE line that also runs to the embedded YM2612, so tying it to ground would effectively ground the internal signal and prevent the internal YM2612 from receiving writes. PSG would still work, but YM2612 communication would be interrupted. That's good to know. That might also apply for the other three lines, I/O, ZTOV, and VTOZ. If that's the case, it might be possible to effectively disable the I/O region, and M68000-Z80 or Z80-M68000 bus access by grounding these other pins.

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Post by TmEE co.(TM) » Thu May 24, 2012 7:07 pm

Problem is that those pins are driven inside the chip, and driving them externally will hurt the insides.
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Post by Nemesis » Thu May 24, 2012 11:23 pm

Fair enough then. So, if you want to disable those features permanantly, as in forever, then ground those pins. lol

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Re: Sega TeraDrive motherboard pics

Post by piroxilin » Tue Mar 22, 2016 9:14 pm


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Re: Sega TeraDrive motherboard pics

Post by Sik » Wed Mar 23, 2016 12:22 am

piroxilin wrote:BIOS of teradrive : http://piroxilin.narod.ru/sega/teradriv ... 27c010.bin
And here I was hoping I was gonna get some work stuff done. There goes the day...

EDIT: oh, it's the PC BIOS. I wonder if it includes any Tera Drive specific code or not.

EDIT 2: by the way before I forget, looks like this thing is actually two 64KB ROMs (I guess they were contiguous segments in the address space). If you see a gap full of 0xCC, this is why - that's the padding at the end of the first ROM.
Sik is pronounced as "seek", not as "sick".

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Re: Sega TeraDrive motherboard pics

Post by piroxilin » Wed Mar 23, 2016 6:50 pm

On the board, there is one more ROM - "HN 62414".
-del-
But remains a mystery which contains "ROMDISK"?
All files with the "PC-DOS" occupy 150KB, and even zipped - 80k.
And they are definitely not in the main BIOS.
Now I'm looking for an option how to read the mask ROM (16*512k) ...
Last edited by piroxilin on Fri Mar 25, 2016 11:41 pm, edited 2 times in total.

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Re: Sega TeraDrive motherboard pics

Post by piroxilin » Fri Mar 25, 2016 11:16 pm

Yay!!

I read it it via an adapter qfp44-dip42. http://piroxilin.narod.ru/sega/teradriv ... 27c800.jpg
U38 (HN62414) contained ROMDISK!
ROMDISK DUMP : http://piroxilin.narod.ru/sega/teradrive/tru-27c800.bin
Chip HN62414 (512k*16bit) sheet : http://piroxilin.narod.ru/sega/teradrive/hn62xxx.pdf

PS.
In Teradrive, Z80 have 16KB of SRAM (2 x m5m5165).

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Re: Sega TeraDrive motherboard pics

Post by Sik » Sat Mar 26, 2016 12:28 am

Yeah the 16KB of Z80 RAM is mentioned by Sega in their Tera Drive page. What they never mention though is how much work RAM the system has? Or if it's even shared between the x86 and 68000.

Another thing they mention is that the 68000 runs at "10MHz / 7.67MHz". I guess it can run the 68000 at two different speeds (and 10MHz is used for the x86 side of things too) but I wonder how does it select which clock to use?
Sik is pronounced as "seek", not as "sick".

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Re: Sega TeraDrive motherboard pics

Post by Huge » Sat Mar 26, 2016 7:27 pm

Sik wrote:
piroxilin wrote:BIOS of teradrive : http://piroxilin.narod.ru/sega/teradriv ... 27c010.bin
And here I was hoping I was gonna get some work stuff done. There goes the day...

EDIT: oh, it's the PC BIOS. I wonder if it includes any Tera Drive specific code or not.

EDIT 2: by the way before I forget, looks like this thing is actually two 64KB ROMs (I guess they were contiguous segments in the address space). If you see a gap full of 0xCC, this is why - that's the padding at the end of the first ROM.
Shane did two teradrive bios dumps a few years back, they were different. I wonder if this one matches either of them.
And yeah, they are standard IBM PC bios files.

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Re: Sega TeraDrive motherboard pics

Post by piroxilin » Sun Mar 27, 2016 11:10 pm

Bios from Shane (MODEL3.BIN) is 512kb and dated 06/04/91. In file only last 128kb is needed. I pub it here : http://piroxilin.narod.ru/sega/teradriv ... 3-128k.bin .
Bios from my teradrive dated 03/22/91 and have a difference. http://piroxilin.narod.ru/sega/teradriv ... 27c010.bin

Teradrive without romdisk chip even not started. Chip is 1MB size, but 1 and 2 halfs is same.
Apparently without initializing, bus switch suppresses any communication.

I repaired his hard drive WDL-330P(dead electronics, the drive is not spinning), uploaded to the history of his bios : http://piroxilin.narod.ru/sega/teradriv ... 27c256.bin

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Re: Sega TeraDrive motherboard pics

Post by piroxilin » Sun Jul 23, 2017 10:20 pm

After all i connect sega-cd to my amstrad mega-pc.

proof: https://youtu.be/X6q1VmEBfr8

I buy my mega-pc on ebay in very bad condition.
After repair and some upgrades it work fine with sega-cd :)
repair :
dead system controller 76c010
dead and leaked battery
removed recaped capactors
dead VIA pads on sega side
no sound - bad tracers
broken button on cartridge slot (sega power-on)
broken FDD (dead step motor)
invalid HDD (80GB!!!)

Upgrades:
added new 4 simm-30 sockets and 2mb ram (6mb overal)
added internal palcoder for RCA out (video, R, L)
installed 530MB HDD
changed FDD.

----------

some fotos : https://vk.com/album96271606_245412790

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