Mr.Do Save High Score & Screen Flip

Here's the scoop on making Mr.Do save it's high-score table, and in addition FLIP the screen ! I just put this page together quickly after I finished hacking the ROMs, so it doesnt look the pretiest in the world, but anyway here's how to do it...

Getting Mr.DO to save the high-score table was much easier than Galaga, for a start the board already uses 2k x 8 Static RAMs, so you can just replace the HM6116's, located at H4, with the Dallas battery backed parts.  The only downside here was on my board, and at least 4 others I've checked, the RAMs were not socketed, so a little soldering needs to be performed.

The second step is the modified program ROM, this will stop the normal power on from clearing the high-score table and re-initializing it with the default values, however when the game goes into test mode then the high score table is erased, that seemed fair.

The second BIG thing was not high-score related, the monitor in Mr.Do is inverted, so running it in one of my standard cabinets, the screen is the wrong way up ! Very annoying, the game does not support a flip screen via a DIP switch, so I had to modify the program code to support flip screen. To do this I replaced the DIP switch for "rack advance" with a flip screen function, set the switch 'ON' the screen will be inverted.

I'm going to have a look at getting the between level, animations to move in the correct directions with the flip enabled, this doesnt distract from game play but would be nice to make the flip upgrade perfect.

If you dont use the flip feature then everything on the board, apart from rack advance, works as normal.

Two of the game program ROMs have been modified, you will need to replace these to implement save hi-score and screen flip, the ROMs are 2764, or 27C64, these are 8k x 8 EPROMs.

Game Enhancements

1. Save high-score
2. Flip-screen funtion, replaces "Rack Advance"  DIP switch A, 5
   
   *NOTE*  You do not need to add the RAM for just the screen flip.

Known issues

1. Title screen, the colored background behind the Mr.Do logo, starts, disappears, then starts again. 
   Bug caused by the flip.
2. Between level animations, the characters move in the wrong direction !! 
   This is caused by the flip.
3. Test mode clears the High Score RAM.
   

Upgrading

You will need, 1 x 24pin socket, 2 x 2764 EPROMs, 1 x DS1220AB static RAM -there's an alternative SGS Thompson part M48Z02 which should also work. This is a 2k x 8 battery backed static RAM.
Skips steps 1 & 2 for just the flip screen.

1. Remove RAM at location H4, if not socketed then de-solder and put in a socket.
2. Replace the RAM at location H4 with the non-volatile SRAM.
3. Burn two new EPROMs using the images below, these replace the program ROMs at board locations A4 and C4.
4. Power up the game and hey presto, high-scores are saved AND you can flip the screen.

Download Modified Program ROMs Replacement A4 & C4

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