TTL HEX LED driver chip

[Doug Jackson]

>
> Sure, the Fairchild 9370, 9368 and 9374.  All include a latch (a nice 
> feature).
>
> --Chuck
Heh heh.

This reminded me of a project I did in a hardware interfacing class a 
very long time ago.

The project was to interface two 7 segment displays to a single 8 bit 
I/O port - The design specs required that the displays should be able to 
show hex characters, and be turned off - It was clear that the *intent* 
of the assignment was that we were supposed to be learning about 
scanning displays.

My lecturer was very surprised when I turned in a PCB with two 7 segment 
displays, and two 9374 chips.  I tied the data lines together, and 
brought the individual latch and Ripple Blanking lines out - two port 
writes were all that was required to display anything - and there was 
none of that messy scanning required to keep the display updated.  Using 
the ripple blanking inputs, allowed me to turn off each display 
individually.

I got an A, and the assignment sheet was updated to prevent the solution 
in the future!!

Doug Jackson