At 12:15 PM 6/14/02 -0700, Brendan Moran wrote:
>I'm trying to decode 2 16-bit hex numbers to BCD then display them on
>7-segment displays from a '877.
>
>What I'm thinking right now is setting up a few 22v10's to act as
>combination BCD to 7-segment decoders and latches, and using them to
>handle everything.

Shift registers!  If you want to run the LED displays from the unregulated
supply, use TPIC6595 (1 per digit).  If you can afford to burn power from
your regulated supply, 74hc595.

If I am doing only a few displays, I use the TPIC part and run the displays
from the unregulated supply.  That lets me use a nice small regulator
(LP2950) and spread the power dissipation over a larger area (the segment
resistors for the LEDs).  I almost always wind up using 8 pin SIP resistor
packs for the segment resistors.

On boards that have LOTS of LEDs, I use a NS simple switcher set at 4.0 Vdc
(nice brightness with 100R SIPs) for the LED supply and use 74hc595 shift
registers.

All this takes very little code in your PIC and only 3 output pins.  And
the shift registers cost MUCH less than the 22v10's.

dwayne

--
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

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