Normally I would say (1) would work great, but some games now are using this display to display spinner counters or other information. Also, that display isn't consistent across all games, sometimes it's shifted IIRC.

(2) would work great for non-stern mpu200 games that display the hstd at the start of the last ball.

Can you tap into other signals like the ball in play lamp or strictly the display signals? You could have a sense wire to the ball in play lamp, when it's lit, you're in a game (unless you're in lamp test)

Or the game over lamp of course.

I've checked all my bally games and nothing seems to use the ball counter digit when a game is in progress, i.e. they all show 1,2,3,4,5 etc for the ball in play</blockquote

There are some rom mods that use it both original board and Arduino add ins.

This is a downside of having two interrupts.... The score blinking timer is in the zero cross so isn't going to sync with the display interrupt.

If you can handle different display refresh frequencies you should be fine. I'd assume you're triggering off what the actual displays do (the blanking/strobe/data lines).

That's odd, I know they set up/send the data in a different way (especially on mpu200 games) but wouldn't it/shouldn't it be a hardware thing since you can only activate displays via the bcd data and the strobe?

Incidentally, it would be interesting if you had your decoder be able to take actual alpha characters as well, as BSOS could be modified to send ascii instead of bcd (as I'm sure mpu200 games could be modified as well for the same reason). This would also open up being able to make a display panel for system 11 games like Rolpa is working on: https://pinside.com/pinball/forum/topic/wip-project-drop-in-animated-color-display-for-williams-an-games#post-6930828

BSOS is coming for system 11:

I've run into that 3 line bcd control scheme before although it was for a different reason.... prototyped some software for it but it never went into production so I'm not sure it even ever worked.

When you say flashing you mean blinking the display? Although the capability is in the software for mpu200 to have the 'player5' (credit) display blink, I don't think they ever did it intentionally. The player score display blinking when the score timeout timer is idle. Every score resets it to #$FF and when it hits zero it runs a flip mask routine for the currently up player, along with setting another timer (much shorter I forget the period) to flip it back. They just OR the mask in with the bcd digit in the display interrupt. The actual timers and display mask update are done in the zero cross.

yep, kind of nicer vs. the 2:3 decoder scheme Oliver came up with way back when (although that is now built into weebly boards)

Wiring/triggering is the same as Bally or the software wouldn't be cross compatible. I think if you're duplicating what the decoder chip on the display is doing it should be able to grab the info.

How long are you waiting before grabbing the digit info? Propagation delay should be really low here; when I was fooling around with making a wav trigger type sound board 12-13 years ago, I had a really hard time getting an arduino to grab the byte correctly and ended up using the same logic latches the sb-100 sound board used, and reading the data off the latch instead of the data bus directly.

I guess you are doing similar, populating the shift register directly and reading it from the microcontroller? I wonder if the shift register's logic threshold is affecting this if dothedoo 's levels happen to be too low to indicate logical 1? (I forget exactly the details, but don't different parts cmos vs. ttl have differing logic levels?)

Some of the games use the other digits (orbitor 1, dragonfist, possibly a couple others)

http://www.pinball4you.ch/okaegi/pro_d7.html

I assumed he meant non-playing players' displays which are completely blank on some titles on non 4 player games.

That 00 sitting there on those early games when they aren't playing drove me crazy! Especially since the Bally OS had it built in to do it either way... show the 00 for non playing players, or don't.