Brooke wrote:

> I would like to use a few 74HC595 shift registers to get 24 bits
> of latched data output.  Could someone help me with the correct
> Brooke

Brooke, I don't have a description of the 74HC595 in front of me as I
write this... However, I have used shift registers to expand PIC output
capacity sucessfully in the past. Using 2 PIC output pins (clk and data)
you can cascade (msb of lower SR to input of higher SR) as many Shift
Registers as you like. Use port B outputs so that their internal pullups
are present when the PIC is in reset.

One little trick that I used to get all SR outputs to change at the same
time was to wire the clk line to a diode and resistor in parallel,
connected to the SR output update pin, with a capacitor on this pin
connected to ground. When the clk went idle (after clocking in all of
the SR bits) the update line would assert. I needed the synchronous
output feature because the SR drove a resistor network/op amp ADC.

If you need additional info on this please let me know.

--
Regards, Dana Frank Raymond