Forums

Sega Master System / Mark III / Game Gear
SG-1000 / SC-3000 / SF-7000 / OMV
Home - Forums - Games - Scans - Maps - Cheats - Credits
Music - Videos - Development - Hacks - Translations - Homebrew

View topic - Sega 315-5066 pinouts (custom chip in SG-1000 II)

Reply to topic
Author Message
  • Joined: 03 Oct 2011
  • Posts: 179
  • Location: New Zealand
Reply with quote
Sega 315-5066 pinouts (custom chip in SG-1000 II)
Post Posted: Sun Nov 27, 2011 3:09 am
Last edited by honestbob on Wed Nov 30, 2011 9:37 pm; edited 5 times in total
Hi All

Here are the pinouts for the Sega 315-5066 chip in the SG-1000 II. This is a combination TMS99XX compatible video chip and SN76489 sound chip all rolled into one.

Sega 315-5066 pinout

Note: IC11 and IC12 are NEC D41416C-15 - 16K x 4 DRAM. This provides the 16K of VRAM for the 315-5066 chip. Pin 1 /OE is permanently wired low.

Note 2: NC means 'Not Connected', although it is hard to be certain on that as the board has a second layer of white soldermask or silkscreen on top of the green soldermask, so it is hard to see which traces go to which IC pins.

Note 3: There are several outputs for the custom RGB signals which go to unused solder points on the PCB so it looks like you can modify to suit other video systems if you know what you are doing (currently NTSC RF).

Note 4: There is also a component labelled IO 73863 T.Q.C. connected to the 315-5066 and I have no idea what that is :)
[Edit - this is a 10.73863 MHz crystal oscillator]

1: pin 2 IC 11 I/O1 (VRAM)
2: pin 3 IC 11 I/O2 (VRAM)
3: pin 15 IC 11 I/O3 (VRAM)
4: pin 17 IC 11 I/04 (VRAM)
5: pin 2 IC 12 I/O1 (VRAM)
6: pin 3 IC 12 I/O2 (VRAM)
7: pin 15 IC 12 I/O3 (VRAM)
8: pin 17 IC 12 I/O4 (VRAM)
9: GND
10: pin 4 of RF modulator (audio output)
11: +5v
12: pin 1 input to LS32 also pin 11 on expansion edge connector
(the other input is Z80 /RD)
the output of this feeds into pin 4 on the LS32 and that is ORed with
input from pin 22 on the Expansion edge connector. The output of that
goes to pin 15 on IC8 LS257
13: NC
14: NC
15: NC
16: NC
17: NC
18: pin 13 LS32 OR gate (ORed with DSRAM to give the /CE for 2KB onboard SRAM)
19: /CEROM2 signal to cartridge port pin B04
20: input from RESET / Hold switch
21: Z80 /NMI (pin 17)
22: Z80 /MREQ (pin 19)
23: C1 + lead, /RESET Z80 (pin 26)
24: Z80 /RFSH (pin 28)
25: Z80 A14
26: Z80 A15 (pin 5)
27: R on PCB (unused solder point)
28: G on PCB (unused solder point)
29: B on PCB (unused solder point)
30: composite video output for RF Modulator pin 3
connected to TP1 on PCB (unused solder point), R40 127 ohm pull down resistor to GND, C16 + lead
pin 3 of the RF Modulator is connected to the negative lead of C16
31: CSYNC on PCB (unused solder point)
32: GND
33: 10.73863 MHz crysal oscillator. Right pin when looking from component side of PCB
34: other lead of 10.73863 MHz crysal oscillator , C12
35: Z80 /CLK (pin 6)
36: pin 5 IC11 & IC12 /RAS (VRAM)
37: pin 16 IC11 & IC12 /CAS (VRAM)
38: pin 4 IC11 & IC12 /WE (VRAM)
39: pin 14 IC11 & IC12 A0 (VRAM)
40: pin 13 IC11 & IC12 A1 (VRAM)
41: pin 12 IC11 & IC12 A2 (VRAM)
42: pin 11 IC11 & IC12 A3 (VRAM)
43: pin 8 IC11 & IC12 A4 (VRAM)
44: pin 7 IC11 & IC12 A5 (VRAM)
45: pin 6 IC11 & IC12 A6 (VRAM)
46: pin 10 IC11 & IC12 A7 (VRAM)
47: +5v
48: VQO on PCB (unused solder point)
49: GND
50: pin 10 on expansion connector /RD
51: pin 9 on expansion connector /WR
52: pin 7 on expansion connector /IOREQ
53: Z80 A0 and pin 1 of both LS257s
54: Z80 A6 (cartridge A07)
55: Z80 A7
56: Z80 /INT (pin 16)
57: Z80 D0
58: Z80 D1
59: Z80 D2
60: Z80 D3
61: Z80 D4
62: Z80 D5
63: Z80 D6
64: Z80 D7
  View user's profile Send private message Visit poster's website
  • Joined: 28 Sep 1999
  • Posts: 1156
Reply with quote
Post Posted: Tue Nov 29, 2011 2:11 am
Quote
There is also a component labelled IO 73863 T.Q.C. connected to the 315-5066


This weird looking thing is a 10.73863 MHz crystal oscillator.

Quote
12: pin 1 input to LS32 also pin 11 on expansion edge connector
(the other input is Z80 /RD)
the output of this feeds into pin 4 on the LS32 and that is ORed with
input from pin 22 on the Expansion edge connector. The output of that
goes to pin 15 on IC8 LS257


On the expansion connector pin 11 is KBSEL#, so that would make pin 22 the active-high joystick port disable signal (JYDS/KILLGA).

The pair of '257s likely makes up the input ports then, with the select input coming from A0 to decode pairs like C0/C1 or DC/DD.

This is fascinating as it is identical to the I/O implementation in the Mark III. You can really see the evolution of the SG-1000 becoming the Mark III with this system.

Quote
53: pin 1 of both LS257s

This is probably Z80 A0.

It seems like there is no composite video output, so I guess there must be components on the board to do RGB to composite conversion to feed the RF modulator?

Thanks for doing all this hard work!
  View user's profile Send private message Visit poster's website
  • Joined: 03 Oct 2011
  • Posts: 179
  • Location: New Zealand
Reply with quote
SG-1000 II Photos and 315-5066 Pinout Corrections
Post Posted: Tue Nov 29, 2011 5:45 pm
Last edited by honestbob on Wed Nov 30, 2011 9:42 pm; edited 1 time in total
Quote
This is probably Z80 A0


Correct. Pin 53 is also connected to Z80 A0 (pin 30)

Quote
This weird looking thing is a 10.73863 MHz crystal oscillator.


Thanks. On reflection that does look like a '10' rather than 'IO'. Oops :)

Quote
It seems like there is no composite video output, so I guess there must be components on the board to do RGB to composite conversion to feed the RF modulator?


I originally had pin 10 as NC. This in fact feeds to the RF modulator, so I'd guess this is the composite video output. Those unused solder points on the board with the seperate RGB signals etc. are not connected to the RF modulator. I guess this was Sega working on a single chip which could be used for all markets with some external hardware mods?

pin 1 of rf modulator goes to high / low channel switch

pin 2 of rf modulator is +5v

pin 3 of rf modulator is R41 330 ohm (which goes to C16 negative lead) and is in series with R42 1760 ohm to GND. The positive side of C16 is that unused TP1 solder point which is connected to pin 30 on the 315-5066.

[Edit - this is the composite video feed from the Sega 315-5066 pin 30]

pin 4 of rf modulator goes to pin 10 of Sega 315-5066

[Edit - this is the audio feed]

I will correct the original post.

Quote
Thanks for doing all this hard work!


No worries :)

I managed to get the heat shield off, so here is another piccy showing the RF modulator, plus better high res photos of the SG-1000 II PCB.

And just for reference, here are the continuity tests I did on the expansion port

SG-1000 II Expansion Port Pinout
1: GND
2: GND
3: GND
4: GND
5: Z80 A2
6: NC
7: /IOREQ
8: CONT
9: /WR
10: /RD
11: pin 12 on Sega 315-5066 and pin 1 on OR gate
12: D7
13: D6
14: D5
15: D4
16: D3
17: D2
18: D1
19: D0
20: A1
21: A0
22: from pin 5 of LS32 OR gate (input) (OR gate pin 6 output goes to pin 15 on IC8 LS257)
the other input is pin 1 OR pin 2
pin 1 is from pin 12 of Sega 315-5066 chip. pin 2 is /RD
23: +5v
24: +5v
SG1000_II_09_under_heat_shield_smaller.JPG (921.48 KB)
SG-1000 II PCB - heat shield removed. RF Modulator visible.
SG1000_II_09_under_heat_shield_smaller.JPG
SG1000_II_PCB_Top.JPG (969.69 KB)
SG-1000 II PCB Top View High Res
SG1000_II_PCB_Top.JPG
SG1000_II_PCB_bottom.JPG (1012.7 KB)
SG-1000 II PCB Bottom High Res
SG1000_II_PCB_bottom.JPG

  View user's profile Send private message Visit poster's website
  • Joined: 28 Sep 1999
  • Posts: 1156
Reply with quote
Post Posted: Tue Nov 29, 2011 7:09 pm
Quote
I originally had pin 10 as NC. This in fact feeds to the RF modulator, so I'd guess this is the composite video output. Those unused solder points on the board with the seperate RGB signals etc. are not connected to the RF modulator.


If pin 10 is the composite video output, then I guess pin 30 is the audio output (just judging by the caps and stuff attached to it).

Quote
I guess this was Sega working on a single chip which could be used for all markets with some external hardware mods?


It could be. The composite video output would definitely not work if there was a PAL mode, but in that case the RGB output could be used. I don't know if there is any easy way to determine which pin is a potential NTSC/PAL select input. It may not even have one.

Quote

I managed to get the heat shield off, so here is another piccy showing the RF modulator, plus better high res photos of the SG-1000 II PCB.


Very nice, I was wondering where the other '257 was at.

Quote
And just for reference, here are the continuity tests I did on the expansion port


Good to see this is compatible with the MK3 expansion port.

If you've had a chance to look at the cartridge port, does Z80 /M1 go to pin B20? No rush though, you've done plenty already. :)
  View user's profile Send private message Visit poster's website
  • Joined: 03 Oct 2011
  • Posts: 179
  • Location: New Zealand
Reply with quote
Post Posted: Tue Nov 29, 2011 8:25 pm
Quote
If you've had a chance to look at the cartridge port, does Z80 /M1 go to pin B20?


I posted the cartridge port connections on your original pinout thread that I side-tracked into a discussion on the SC-3000 keyboard :) See the last post on

http://www.smspower.org/forums/viewtopic.php?t=13371

I have B20 as NC, but I will recheck that tonight.

[Edit - correct. B20 is not connected to anything]

Quote
If pin 10 is the composite video output, then I guess pin 30 is the audio output (just judging by the caps and stuff attached to it).


I wondered about that. The only issue is that pin 30 on the 315-5066 is connected to the positive lead of C16 and pin 3 of the RF modulator is connected to the negative lead of C16 through R41, but there are no direct connections between pin 30 on the 315-5066 and the RF modulator. I thought the main purpose of caps in general was a smoothing effect, so that couldn't be used to transmit the audio signal to the RF modulator, right? Or could the audio signal already be encoded in the output from pin 10? Does anyone know what pin 3 and pin 4 on the modulator are supposed to do? I can't find a datasheet for this modulator.

[Edit - we've obviously hit the limits on my understanding of basic electronics :) But I think I see how the link from pin 30 to the modulator works - I'm guessing the cap and resistors together work to translate the digital signal to some sort of analog waveform input into the modulator. Anyone with a better grasp of electronic circuits please feel free to correct]

Those pin 3 connections to the RF modulator didn't make much sense to me when I looked at it this morning, so I will recheck those connections tonight to see if I've missed anything.

[Edit - yes, that is how it is wired up. Nothing else seems to be connected to pin 30 of the 315-5066 or to pin 3 of the rf modulator. The only other bit I missed is that the rf modulator case mount points provide the ground signal to the modulator, so pin 3 & 4 are the only inputs AFAIK)

Cheers
  View user's profile Send private message Visit poster's website
  • Joined: 28 Sep 1999
  • Posts: 1156
Reply with quote
Post Posted: Wed Nov 30, 2011 5:43 pm
Quote
[Edit - correct. B20 is not connected to anything]


OK, thanks for confirming that and documenting the cartridge pin connections. I wrote that B30 was connected to /M1 for the SC-1000 in the pin list, but now I find that highly suspect. I'll examine the PCB scan again and double check the connections.

Quote
[Edit - we've obviously hit the limits on my understanding of basic electronics :) But I think I see how the link from pin 30 to the modulator works - I'm guessing the cap and resistors together work to translate the digital signal to some sort of analog waveform input into the modulator. Anyone with a better grasp of electronic circuits please feel free to correct]


IIRC for AC signals the capacitor removes the DC offset. This is referred to as AC coupling (series capacitor on the output) as opposed to DC coupling (no cap). For consumer audio/video equipment it's all AC coupled I believe.

Quote
Edit - yes, that is how it is wired up. Nothing else seems to be connected to pin 30 of the 315-5066 or to pin 3 of the rf modulator. The only other bit I missed is that the rf modulator case mount points provide the ground signal to the modulator, so pin 3 & 4 are the only inputs AFAIK)


This sounds right. Check out the RF modulator in the SMS schematic:

http://cgfm2.emuviews.com/img/master.gif

It seems to be configured the same way you described, there's a composite video, monaural audio, and +5V input, and the case is used for ground.
  View user's profile Send private message Visit poster's website
  • Joined: 03 Oct 2011
  • Posts: 179
  • Location: New Zealand
Reply with quote
Post Posted: Wed Nov 30, 2011 8:31 pm
Quote
IIRC for AC signals the capacitor removes the DC offset. This is referred to as AC coupling (series capacitor on the output) as opposed to DC coupling (no cap). For consumer audio/video equipment it's all AC coupled I believe.


Thanks. That gives me enough to do a web search to learn more about it :)

Quote
Check out the RF modulator in the SMS schematic: It seems to be configured the same way you described, there's a composite video, monaural audio, and +5V input, and the case is used for ground.


On the SMS schematic, pin 3 is video and pin 4 is the audio feed to modulator. Care to take a guess on which is which on the SG-1000 II? Or do I need to post a photo of the internals of the modulator to be sure? Can you pop the top on those easily with a screwdriver? It looks like it is just crimped on.

Also see PCB photo below with labelled connections from 315-5066 to RF Modulator
SG1000_II_RFModulatorPCBLabelled.jpg (169.54 KB)
SG-1000 II PCB - labelled connections from 315-5066 to rf modulator
SG1000_II_RFModulatorPCBLabelled.jpg

  View user's profile Send private message Visit poster's website
  • Joined: 28 Sep 1999
  • Posts: 1156
Reply with quote
Post Posted: Wed Nov 30, 2011 9:13 pm
Quote
Care to take a guess on which is which on the SG-1000 II? Or do I need to post a photo of the internals of the modulator to be sure? Can you pop the top on those easily with a screwdriver? It looks like it is just crimped on.


The inside of the RF modulator is very cramped and complicated, so it may be hard to figure out what's what. The top just pops off, though you may need to bend it back into shape to fit it back on securely.

I'm not sure which pin is which on the modulator myself. I suppose narrowing it down to two pins is good enough for trial and error testing when somebody reads this thread while attempting a video mod of some kind.
  View user's profile Send private message Visit poster's website
  • Joined: 03 Oct 2011
  • Posts: 179
  • Location: New Zealand
Reply with quote
Post Posted: Wed Nov 30, 2011 9:30 pm
Quote
I suppose narrowing it down to two pins is good enough for trial and error testing when somebody reads this thread while attempting a video mod of some kind.


Works for me :) I'll leave the modulator alone then.
  View user's profile Send private message Visit poster's website
  • Joined: 03 Oct 2011
  • Posts: 179
  • Location: New Zealand
Reply with quote
Post Posted: Wed Nov 30, 2011 9:36 pm
I just checked that RGB Mod page.

http://translate.google.com/translate?sl=ja&tl=en&js=n&prev=_t&h...

Quote
C-SYNC (C-Video) instead of C-SYNC, pin 3 of the RF unit
Pin 4 of the RF unit speech


So pin 10 on the 315-5066 is audio, pin 30 on the 315-5066 is the composite video feed.
  View user's profile Send private message Visit poster's website
  • Joined: 28 Sep 1999
  • Posts: 1156
Reply with quote
Post Posted: Thu Dec 01, 2011 1:20 am
It's weird, I checked again and pin B20 really is /M1 on the SG-1000. I used these two pictures to confirm:

http://www.smspower.org/misc/sg1000-01.jpg
http://www.smspower.org/misc/sg1000-02.jpg

It's strange they'd assign /M1 like this for the SG-1000 only, then leave it unused for the SC-3000, SG-1000 II, and Mark-III, only restoring it for the Japanese SMS.

I'll update the pinouts.csv file with your contributions and a footnote about this oddity. :D
  View user's profile Send private message Visit poster's website
  • Joined: 25 Feb 2013
  • Posts: 223
  • Location: Osaka
Reply with quote
Post Posted: Sun Oct 18, 2020 7:31 am
Thank you for all the tracing, I attach a schematic for future reference
sg1000video.pdf (37.79 KB)

  View user's profile Send private message
Reply to topic



Back to the top of this page

Back to SMS Power!