74HC74 sega master system1 switchless trouble.

Seeing as this is a SMS 1,and if the rest button method is non workable,what about trying to use the SMS's pause button ?

 

Is that maybe why my 7474 LED would toggle only when i powered the SMS on ?

 

I find this strange as far as I am aware, the RESET button on the SMS is software driven.

The RESET pin on the console is just a bit on a I/O port which have as purpose:

Prevent games from being reset if they're already at their title screens

Prevent the SMS1 SEGA logo from BOOT ROM from being displayed every time RESET is pressed. If you issue an POR it will display the SEGA LOGO.

If you issue an POR on a MD console it will display the "Produced by or under licence from SEGA ENTERPRISES." message. If you just press reset it won't (but MD reset is actually reseting the 68000 by hardware)


Have you tried to add an pullup to the RESET button ?

 

Well, i connected up Q directly to the LED anode and to the SMS's signal and the cathode of the LED (through a POT set to just over 300 ohms)to Vss and everything works .:thumbsup:

Wow ,the first bit of good news ,excellent now if we can make it 2 for 2 with the reset/pause button to toggle the regions .

 

About the mega drive point,on the original model 1 version,there are two versions of this console,one where if the reset button is pressed ,it sends a vss signal ,and the other model one pcb version sends Vcc when the reset button is pressed!

With Calpis's circuit ?

 

What are you both using to draw these circuit schematics ?

 

I am using this:
http://www.suigyodo.com/online/e/

Suggestion from Lawrence at NFG:

http://nfggames.com/forum2/index.php

Direct link to the thread:
http://nfggames.com/forum2/index.php?topic=3735.0

Great stuff :thumbsup:

 

I think you should add this to the gamesX wiki ? No need to buy and flash a PIC either.

 

Register there yourself and feel free to contribute.

Lawrence and Kendrick aways welcome contributions to their wiki. :thumbsup:

Also both are fellow users of ASSEMbler games forums as well

By the way, I use that circuit on my SEGA Saturn to switch it from Japan to USA (It defaults to Japan) and on my Mega Drive (also defaults to Japan)

 

That bit of software you recommended is dot on like.

 

To get you the english or japanese mode working .Instead of using an external switch,it can be wired to the pause button instead,as when you press it,it gets grounded i assume.

So apply this with the 50/60 hz speed mod and you now have a great multi system master system,without hacking up the casing!

Just keep the pause button held before you switch on and let go a few seconds after the sega logo.