New mod released. The Master System RGB Encoder Switcher is designed to allow a Master System to be modded for true PAL and true NTSC. It provides a way to switch the RGB Encoder, usually a CXA1145P or MB3514, between PAL and NTSC operating modes via Pin 7, and route the correct subcarrier clock to Pin 6. For the first time ever it is possible to have a real PAL and real NTSC Master System in one.
How Does the RGB Encoder Switcher Work?
It’s very simple.
1 – Re-routing clock signals
A PAL system creates the correct PAL subcarrier clock by default and by using a DFO, the Z80 clock will match that of the NTSC subcarrier clock when in NTSC mode. The mod takes the Z80 clock and the PAL subcarrier clock and sends them into a multiplexer. A switchless region mod will switch the multiplexer between these two inputs so only one is output to Pin 6 of the RGB Encoder.
2 – Inverting the region switch signal
The Master System VDP region setting is the opposite of the RGB Encoder region setting. So an inverter is used to flip the control signal so the RGB Encoder and the VDP regions will match.
RGB Encoder – CXA1145P/MB3514 Pin 7
- Low = PAL
- High = NTSC
The Master System – VDP Pin 57
- Low = 60Hz
- High = 50Hz
Because of this the standard switch output of a Master System region mod can not switch the RGB Encoder to match the region of the console. So the mod inverts the switch signal so it can be sent to Pin 7 of the RGB Encoder.
That’s it. Just a multiplexer and an inverter.
Why Invent the RGB Encoder Switcher?
1 – Because it was never previously possible to have a genuine PAL and a genuine NTSC Master System in one.
2 – Sometimes it’s fun to play in composite video and this means there is full compatibility with PAL and NTSC TVs.
3 – It was fun to identify a problem, study the system to try work out a solution, then design a brand new mod kit.
Requirements
1 – A way to generate a PAL and NTSC master clock such as a Dual Frequency Oscillator.
2 – A switchless region mod or a physical region switch to simultaneously switch the RGB Encoder Switcher, VDP Pin 57, RGB Encoder Pin 7, and DFO S0 pad.
Compatibility
- Model 2 / PAL / 171-6395A
- Model 2 / PAL / 171-5922A
Others need to be tested but in theory it should work with any Master System that has a Z80 CPU, a SEGA 315-5237 IO IC, and a 4 pin master clock oscillator.
Mod Kit Variations
There are two versions of this mod kit.
1 – A quick solder board (QSB) PCB version that solders beneath the Z80 CPU.
2 – A standard miniature PCB version which will need fully wiring. This version is intended for experimentation and checking console revision compatibility.
RGB Encoder Switcher Availability
The Sega Master System RGB Encoder Switcher has been released free to the community.
Download from here – https://github.com/consolesunleashed/sega-master-system-rgb-encoder-switcher
Buy from here – https://www.consolesunleashed.com/product/sega-master-system-rgb-encoder-switcher-mod-kit/