> This design will drive 8 digits and can be easily extended to larger
> digit counts. For 8 digits, the duty cycle is 1:8 which is about as far
> as I like to go, brightness will suffer beyond this point.

An alternative design will drive 8 digits (no DP's) with eight port pins,
eight transistors, eight resistors, and no external chips.  The transistors
are wired as emitter-followers on the PIC's eight port pins and feed the
commons on the eight digits.  Each digit's segment wires connect to the seven
port pins that don't drive that digit's common.  The eight resistors, between
the port pins and the segments, limit the display current.

Assuming the displays are common-anode, you'd use NPN transistors.  To drive
a digit, you set its common wire HIGH, set the appropriate segment wires LOW,
and let the other lines FLOAT.  If you want decimal points, then you can get
9 digits with 9 I/O pins.

By the way, if you're driving fewer than eight digits, you'll only need one
transistor per display.  If you're driving only a few digits and you're using
low-current displays, you may be able to elide the transistors entirely.  In
this case, a common-cathode display drive may be preferred since the PICs are
a little better at sinking than sourcing.