74C925 alternative?

I've never dealt with this company, but your 74C925 does show up in a seach.

Good luck. Richard

Use a programmable logic device or an Arizona Microsystems PIC processor - I'm not far enough into either option to identify a part which comes in the right 16-pin 0.3" dual-in-line package (and it might be difficult to find a programmable logic device with enough buried flip-flops to do the job in an essentially obsolescent package) but somebody will know.

Maxim has some super duper new LED drivers.

Maxim has more vapourware tahn we can all shake a stick at.

Do these LED dirivers include 4-digit counters with multiplexed

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A small microcontroller, however, would be my first choice.

-- JF

Thanks for the replies, however, I asked the question so I could avoid using a microcontroller.

Thinking out loud,

With simple CMOS technology going away, wouldn't it be wise to replace it with something you can get in a few years.

Once you get C code running, going to a smaller uC would be easier the second time.

What ever chip you find today, will be gone next year.

good luck

donald

So you wnat the OP to replace a 16-pin DIP with a 28-pin DIP that Intersil has marked "inactive".

I'd prefer a programmable logic part - the 4-digit counter is not synchronous with the multiplexing logic for the display. Back in 1972 I dealt with this problem by freezing the multipexing clock until any incoming count had rippled through the (asynchronous) counters, which took up to 4usec. This wasn't an elegant solution. With a microcontroller, I guess you'd rely on the interrupt system to capture clock increments that occured at the wrong instant, and you'd keep your interrupt handler short and quick to keep the maximum count rate respectable.

Programmable logic offers true parallel processing, which can be a lot tidier.

Many microcontrollers have built-in timers than be driven from external clock. This isn't truly asynchronous, because the external clock is typically sampled on the internal clock, but it still allows quite fast operation. For speeds

I don't know what you were doing in 1972 - the fact that you haven't yet got past 555's does suggest that you aren't an early adopter - but my toy used TTL logic and Beckman 7-segment fluorescent displays, with a few transistors to handle the voltage swings.

And not a filament in sight (nor any hidden filaments either)

Looked quite neat.

The Beckman displays were flat panel plasma discharge displays, sort of like Nixies but segmented and with the segments all in one plane. You used to seem them on gas pumps until fairly recently as well as some industrial instruments (Simpson had a fairly successful series of instruments that used them). National semi made a biplar driver chip DS8880 or something like that.. ah, here it is:

Best regards, Spehro Pefhany

Not really a correction, for you anyway, as "Fluorescent" wasn't an accurate description. The neon plasma discharge emits light directly.

Anway, a trip down memory lane.

Best regards, Spehro Pefhany

It's a one off.

discharge" discharge mechanism - in a low pressure of some noble gas (probably neon, but I can't be sure) and certainly not fom a filament. There was a small, steady "keep alive" corona discharge hdden behind an opaque bit of the glass front, and the active segments lit up when you hit them with something over 180V, whch would have been around the Passchen minimum for avalanche discharge through neon. Without the keep-alive discharge, fast multiplexing could be chancey - it was an added extra feature in the second generation of the displays.

Agreed. The Beckman displays were nicer than most but the 180V seems to have been unpopular.

use a microcontroller?