Re: [avr-chat] STK500 LEDs

[Joerg Wunsch]

"Graham Davies" <address@hidden> wrote:

>> This is the standard way for driving LEDs, the micro
>> can sink more current than it can source ...

> This isn't really true.

It used to be true by the time the STK500 has been designed.  All the
early AVRs also worked that way (usually being able to sink about
twice the current they could source).  Also keep in mind that the
STK500 was even intended for some MCS51 controllers (AT89S51 IIRC),
and the MCS51 in general can *only* sink current on its outputs, not
source.  They don't have a data direction register but only pullup
resistors and a pull-down output driver transistor.  (At least, that's
what I've read about them.  I never really used MCS51 myself.)

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)