315-5339

[HardWareMan]

Hi all again. I got japan MD. :3 Here is it PCB (IC BD M5 VA1):

And I drew attention to the strange chip in DIP16. It was 315-5339, placed between VDP and Z80. I saw it first time. Here is it:

Google told me just one place. "３１５－５３３９：よくわかんない。（Ｚ８０の関係？プロテクト？リージョン？）初期の奴にはなかった。", wich translated by Google as "315-5339: I do not know well. (Relationship Z80? Protection? Region?) In the early guys did.". Some of my friends found another small info: "315 - 5339 DIP16 RAM refresh and EDCLK generation. Only found in MD1 VA0 and VA1". And I traced its pins:

Code: Select all

1 - GND           16 - +5V
2 - VDP#43  HSYNC 15 - +5V
3 - GND           14 - +5V
4 - VDP#84  VA11  13 - +5V
5 - VDP#45  M3    12 - X
6 - VDP#117 OEO   11 - RAM LCS (IA14)
7 - VDP#52  MCLK  10 - RAM HOE (EOE)
8 - GND            9 - VDP#53  EDCLK

Also, arbiter is 315-5308 and it in QFP-80. In PAL version arbiter is 315-5364 in QFP-100 and has clone ТА-04. What do you think?

[TmEE co.(TM)]

I did a pinout in my JP MD M5 VA1 and I came to a conclusion it is for ED_CLK and PSRAM refresh generator.

My schematic differs from yours, I got pin 11 going to lower RAM A13 and pin 4 going to VDP A14.
I have to recheck the address pins... probably did a mistake

VA2 has 315-5308 in but 315-5339 is replaced with 315-5345. Got to see if its different or same...
VA3 has no 315-5345 anymore, if gets integrated into 315-5364 that repalces the 315-5308.
VA4 is a bugfix of VA3 which has only right channel on mono AV out.

I/O chip remains 315-5309 in all models.

http://www.fileden.com/files/2008/4/21/ ... 1FRONT.jpg
http://www.fileden.com/files/2008/4/21/ ... A1BACK.jpg
http://www.fileden.com/files/2008/4/21/ ... 2FRONT.jpg
http://www.fileden.com/files/2008/4/21/ ... A2BACK.jpg
http://www.fileden.com/files/2008/4/21/ ... 3FRONT.jpg
http://www.fileden.com/files/2008/4/21/ ... A3BACK.jpg

[Charles MacDonald]

I would guess it's an "oops" chip to fix some broken functionality in the bus arbiter chip which they later rectified.

It would be interesting to determine which pins are inputs/outputs and and dump it like a PAL; e.g. run every possible input into it and record the output and then determine what the internal logic is. Assuming it has no internal state, that is.

[Huge]

Excellent comparison pictures... I wonder how many Megadrive models there were total, and what the exact differences were between each model.

And one day, I'm surely going to start building a database on their parts numbers.

[HardWareMan]