When HN users recommended it
1 HN user recommended this in 2022, in one comment.
20072026
Each tall tick is one HN user's first recommendation. A short tick is the same user again. Click a tick to jump to the comment.
1 HN user recommended this in 2022, in one comment.
Each tall tick is one HN user's first recommendation. A short tick is the same user again. Click a tick to jump to the comment.
The LED display driver is interesting in this device. It uses 75492 (still available!) for the digit driver and DS8871 for the segment driver. Except DS8871 is open collector, so it is used to force a segment off. For on, there 100 ohm pull ups. These are just the drivers, the latches are separate.
This is a circuit you want to optimize to reduce cost...
For comparison, here is a Z-80 "membership card". It uses 74LS145 for the decoder/digit driver (driven from a counter) and 74HC273 for latch+segment driver.
http://www.sunrise-ev.com/photos/z80/zmc-manual.pdf
The famous KIM-1 uses discrete transistors:
http://www.zimmers.net/anonftp/pub/cbm/schematics/kim-1/kim....
A really modern device might use an integrated LED driver, like TM1637 or TM1638:
https://www.amazon.com/dp/B01D140BT6/ref=sspa_dk_detail_0?ps...