Need guidance on sniffing an old vacuum fluorescent display (VFD)

[unscriptedeng]

I have an old board with a micro running at 8 MHz. Attached you will see display, the schematic, and the ascii characters it uses. The board has an extra connector to connect another VFD. I would like to use this connector to sniff the data going to VFD and use this data elsewhere. First I'd like to see the data via serial print. I think it uses the 8-bit protocol. Is this possible with the Arduino Nano? Can I connect the ports directly and just read them? The VFD has a "Busy" pin which during a falling edge I think data can be read. I would appreciate any guidance as to how to read these pins correctly. Most of the examples I find is about the Hitachi LCD and I have not had success with it.

Note: As I'm a new user it seems like I'm not allowed to upload more than one attachment.

[anon57585045]

WR is a latch pin, so maybe latch the data in a 74HC series buffer/latch IC, use WR to trigger an external interrupt to the Arduino, and read the data from the latch.

Basically, this way, the data is sent to the display and to the latch at the same time. You might want to scope WR to make sure there is enough time between latch command edges to run the ISR to collect the data.

I suggest the latch hardware because (I assume) the hold time on D0-D7 is unknown.

[lastchancename]

It looks like a cash register display module.
With the ‘local’ display, and the optional ‘customer’ display mast.

No problem sniffing those display pins as suggested.
Other than the 8 data bits, no,idea what ‘extra’ pins might be used on that second display.

[unscriptedeng]

I'm actually trying to avoid the latch IC, but as you said hold time on d0-d7 is unknown. I may order some latch ICs to try.

[anon57585045]

Have you scoped it? That should be the first step.

By the way, sniffing an old VFD might be a little bit unpleasant after it's been running warm and collecting dust for several decades...