blinking leds

Hi @ all,
I was able to set up my programmer, so that I can program the at89s51.

I'm trying to get a couple of leds blinking.
Now my question:
Should I connect the leds from VCC to a PORT
or
should I connect the leds from PORT to GND?

Are there any differences/advantages/disadvantages of one method?

sb42

u can do both .. in THIS case there is not much difference (current gets sinked /sourced) . u need to ensure correct polarity of the leds ,max sink/source current (proper resistor) and about open drain o/ps (if i remember correctly x51 has open drain o/p)

Thanks you akg,
I'm trying to get it working now.
sb42