Saturday, 29 December 2012

Dual Boot R-Type 1 & 2 Arcade PCB - Day 4

 Dual Boot R-Type 1 & 2 Arcade PCB - Day 4

Have made progress with the dual-boot electronics, and feel about half way towards finishing the job.!

First I installed three 74LS157 Multiplexers into the three remaining spare chip-sites (lovingly provided by iRem \o/). <3

(The green hoops bring +5v to the chips VCC pins of the 157's - as the top corner pins of the chip-sites are wired to the 5v rail)

Next I wired all the /CS (chip select) pins to ground.. which switches the three chips on permanently..

Then back on the top side; the orange wire carries the game-A/B (0v/5v signal from the hack above), this is wired to the select pins of the multiplexers - which will switch between the R-Type 1 & R-Type 2 signals.

Next I moved the four green wires that went into the board where the tracks were cut (in the original mod (on the left)) to the A0, A1, A2 & A3 inputs of the first multiplexer. These green wires carry the modified R-Type 1 signals.

I then took four yellow wires from the Y0, Y1, Y2 & Y3 outputs to the four points on the board (where the green wires came from)..

Then from below I found 4 board locations that connected to the original four traces that were cut in the original R-Type 1 mod & connected them to the B0, B1, B2 & B3 inputs of the multiplexer.. The red wires carry the original unmodified signals, which are used by R-Type 2.

Upon booting her up, I was greeted with a lovely sight: a nice R-Type 2 boot screen and working backgrounds!! ¦D

Later tonight I'll route the remaining board mods through the second 74LS157 and hopefully bring the sprites back! 
I then plan to use the third chip (if neccesary) to handle the audio Rom selection duties..

Fingers crossed It should all be running this side of the New Year!! :D