That's going to be a tough one Dave.
I wonder if that PAL can be read.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

If the PAL can be read, it can easily be converted to a generic 16V8 GAL format.

Curious Ed...what tool would you use to convert?
PAL2GAL?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

I use my programmer's built in "RAL" relocator software to do it.

Hello Chris,

I've used PAL2GAL to do some conversions. Many times it works great but in some cases that isn't enough. You also need to watch for the speed and brand of the GAL. Helps to have a variety on hand. Had to make one for a memory decoder for a Z80A based processor and had to use a slower rated GAL since the faster one threw off the timing. As long as and original PAL image can be read I could try running a conversion.

Robert

We need someone with a BBB to try to read out the chip.
If the chip fails the aliens will not work properly.
I do not have the code but would also be intrested.

Here is the pcb we are talking about, with the TIBPAL16L8-15CN in the middle.

Untitled (resized).jpg

20180127_083852 (resized).jpg

So it appears that only two inputs (sourced by LM339 channels 1 and 2) and four outputs are used. A 2:4 decoder?

The function is as follows:

IN on the pcb:

12 Volt (for the motors I guess)
5 Volt (for the PAL I guess)
GROUND
Coildriver S30 motor forward
Coildriver S31 motor revers

ON on the pcb
Motor +
Motor -

On switching the game on:
Aliens make 1 round and sit in position

In Testmenu Justage Alien Motor
Motor goes one direction on one speed, according optos check position

In Testmenu Coils
S30 motor moves forward
S31 motor moves backward

In Game , watched this on youtube in slow motion:
Motor works powerfull 1/2 round and stopps apruptly ... balls fall out of the mouth.

If I use a pindora motor emi board:
Switching on the game is okay.
Alien Motor justage works
In test menu *ONLY" move forward works

Could not test in gameplay.

So I guess zje backward and stop function are triggered by this chip.

I think the board, overall is doing the same thing as the circuit described at this link :

https://www.engineersgarage.com/8051-microcontroller/driving-dc-motor-bi-directionaly/

I'm pretty sure BBB uses plain-jane, regular DC motors.

I suspect the PLA is making sure that nothing blows up if both forward and reverse are asserted at the same time.

This is just an educated guess of course. I don't think it is a 2:4 decoder since that's a pretty common, off the shelf part.

With only 2 direction inputs and 4 decoded outputs, there is only so much you can do.

Linked diagram shows it would be a simple decoder -- select neither rotation pair, forward rotation pair or reverse rotation pair. In case of both pair selected - default to...forward, left, none? I would assume none. For that we would need to see what is in the PAL.
It looks like this could have been done with two ICs - a dual 2:4 decoder and a hex inverter. They probably used a PAL to get both low cost ICs into a single IC... saves board space by a bit but would have cost them more per board to make.

An alternate thing this could have done was provide braking for the motor. When it hit stops (as sensed by two LM339 comparators), switch off the motor in that direction. Hard to tell without having schematics.

Looking at it more - the comparators selected which direction it was going. Left or right. There had to be something else to tell it when to start or stop.

"It looks like this could have been done with two ICs"

Agreed .

It definitely looks like the motor driver is an H-Bridge.

I'll be the PAL handles the whole "both FWD and REV" are enabled case (keep the motor off) + simply drives two output pins to enable the forward or reverse side of the H-Bridge. It looks like one of the two outputs has a cap hanging off it to give it a little bit of delay with respect to its partner.

I'm pretty sure you could drive the output of the LM339 to the appropriate inputs of an ST L293D and get the exact same functionality of everything on the PCB in two components and without the PLA (plus some passives of course) .

The ST-Microelectronics L293D is a chip with those 4 big driver transistors integrated into the chip. It also has diodes for that EMP kick that occurs when the motor shuts off. I don't know what the current requirements of the motor are though ... this chip can certainly handle the voltage, but I don't know if it can supply the current . If it can handle it, I'd still heatsink it.

Very intresting informations ! Thank you all !!

On friday a friend comes with a oscilloscope and a homemade motor emi board with test buttons for the directions.
I am sure that he also is reading here and, unlike me, he understands what you write !
Maybe we find a way to pimp up his board with the needet functions !

But I am sure, the code would be helpfull and good to have for the future.

I hope some of the info I posted helps ... I owe you after the BBB failures on my part .

To close this old topic:
meanwhile we found a BBB with this PAL not secured and took a image of it ... for the generatios after us
I send this code to Pfutz, a former programmer from Capcom , who is intrested in this will know how to contact him
My BBB is still running with a normal, active EMI breakboard. There is no really need for the PAL.
I guess the programmers thought: Why do it easy if we can make it complex and complicated .