Sierra Video HDA-109 - Manual (Page 24)

SIERRA VIDEO
18
There are six LEDs that are being driven directly from the PIC32. Each LED is turned on
by bringing the associated PIC output low. The red POWER LED is turned on by the PIC
also but the PIC's output to the LED is inverted by one of the sections of U16. This was
done so that if the PIC doesn't come up the drive output from the PIC will be high
impedance and R71 will pull the input to the U16 inverter high and the output of the
inverter will go low turning on the POWER RED LED. The POWER LED is a special case
since it has both a Red and Green LEDs. There are six conditions that can be indicated
with POWER LEDs using color and flashing sequences.
1. OFF - no power
2. ORANGE - card is starting up
3. Green - card is running with valid input and reference
4. GREEN WITH FLASHING ORANGE - there is a signal error (e. g. missing or
invalid input or reference)
5. RED - card is not operational