To drive the display and read the keypad I need some I/O ports.

The display unit have in total eight anodes and six cathodes that have to be multiplexed by software. So for this I use two 74ALS573 Octal Latches.  One will drive the anodes via resistors (of a rather low value due to the 1:6 muxing ratio) and the horrible source capability of the ALS family, and the other will directly drive the cathodes of the display.

The key matrix are organized as 6 columns x 4 rows, so I'll probably hook up the columns on the keyboard directly to the cathodes of the display and then connect the four rows to the 74ACT245 which is an Octal Bus Transceiver.

It would of course have been better to have an ACT as the display driver since it can both source and sink up to 24mA, but I didn't have one at hand so it is what it is....

Both the '573 and the '245 have a nice pinout structure.  With inputs on one side and outputs on the other side straight over so they are easy to wire up in a bus.  There are some other latches that the input and outputs are net to each other for each the eight internal latches. They are a nightmare to wire up nicely.

Now I just have to figure out where to put in and how to make some decent looking connections to the display/keypad unit...