Sunday, 12 June 2016

Sega Master console

Some future hacking ahead of this wonderful piece of kit.
Thanks to Renee & Wonderboy

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The sounds are classic 1980s chiptune.
...


Little-scale has some excellent info:
http://little-scale.blogspot.com.au/2008/06/how-to-make-32kb-sega-master-system.html

The Japanese Master System used the Yamaha YM2413, aka OPLL.
It's a cost-reduced FM synthesis sound chip manufactured by Yamaha Corporation and based on their YM3812 (OPL2). The FM sound generator uses an 8-Bit data bus to control all of the registers.

I don't have a Japanese version. This uses the following:

CPU
    Zilog Z0840004PSC
This is an 8-bit processor running at 4 MHz.
I/O Controller
    Sega 315-5237
RAM
    NEC D4168C-15 or NEC D4168C-15-SG
VDP
    Sega 315-5246
VRAM
    2 x NEC D4168C-15 or 2 x NEC D4168C-15-SG
Video Encoder
    Sony CXA1145P


It has 8 kB of ROM, 8 kB of RAM and 16 kB of video RAM. Video is provided through an RF switch and displays at a resolution of 256 × 192 pixels.


Sound is provided by the SN76489 PSG (Texas Instruments) chip. The Japanese version also integrates the YM2413 FM chip, which had been an optional feature on the Mark III.

The PSG (programmable sound generator), or PSG, is a sound chip that generates sound waves by synthesizing multiple basic waveforms, and and combining them into more complex waveforms.


The game cartridge slot.

The SN76489 Digital Complex Sound Generator (DCSG) is a TTL-compatible programmable sound generator chip from Texas Instruments. It contains:
  • 3 square wave tone generators.
    • A wide range of frequencies.
    • 16 different volume levels.
  • 1 noise generator.
    • 2 types (white noise and periodic).
    • 3 different frequencies.
    • 16 different volume levels.
 Sega used  modified versions of these sound chips that were incorporated into the system's VDP video display processor. (Sega 315-5246).

 https://moddedbybacteria.wordpress.com/sega-master-system-2-sms/
The above link is very useful.
Audio is tapped off the sega 315-5246 at pin 15.

The pinout info re the rest of the Sega 315-5246 seems to concern video rather than audio.
So attempting to mod this console would probably end in tears for me.:-(
Maybe a better option is to purchase a SN 6849 and build a synth around this.
They are literally "cheap as chips". I bought 5 for under $3.

Some SN76489 synth links:
http://little-scale.blogspot.com.au/2013/02/how-to-build-sn76489-usb-midi-module.html
http://www.instructables.com/id/Squareinator-A-SN76489-Monosynth/
https://github.com/cdodd/teensy-sn76489-midi-synth
http://www.atkinsoft.com/soundgenerators.html

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