Darrel's interrupts in a 7 segment display

[Dave]

Well Actually Steve, The display's may have been wired that way in the schematic originally. Makes no difference. As far as the table is concerned, to generate all 16 hexidecimal characters the table would be 16 entries wide. in the past I have generated tables with all 16 entries as well as lower case "c,n o r". Thats 20. Ther is no standard way if you get my drift. It's completely up to the circuit designer.

[EarlyBird2]

Well Actually Steve, The display's may have been wired that way in the schematic originally. Makes no difference. As far as the table is concerned, to generate all 16 hexidecimal characters the table would be 16 entries wide. in the past I have generated tables with all 16 entries as well as lower case "c,n o r". Thats 20. Ther is no standard way if you get my drift. It's completely up to the circuit designer.

In my post I decoded the lookup table to work out the display pattern and the wiring. I intuitively did not like the resultant pattern and wondered why choose that pattern. Internet searches revealed a commonly followed trend of port.0-port.7 connected to a-g respectively.

From Wikipedia

LED-based 7-segment display which cycles through the common glyphs of the ten decimal numerals and the six hexadecimal "letter digits" (A–F)
Hexadecimal digits can be displayed on seven-segment displays. A combination of uppercase and lowercase letters is used for A–F;[6] this is done to obtain a unique, unambiguous shape for each hexadecimal digit (otherwise, a capital D would look identical to an 0 and a capital B would look identical to an 8). Also the digit 6 must be displayed with the top bar lit to avoid ambiguity with the letter b.

Which implies that there are two ways to wire up a seven segment display one for g-a encoding and one for a-g encoding. But as you say no one has to follow these commonly used encodings, which do dictate the circuit to be used.

The inclusion of "-" and "F" in the encoding makes me think that the original code was probably for displaying temperatures. Also the codes are eight digits which includes the DP reinforcing the idea of a temperature display. I wonder if the original project was wired in the same way, that is assuming this is recycled code.

Can anyone see any advantage in this scheme?

-F-
A E
-C-
D G
-B-

I can not and surely the wiring will be like spaghetti.