I recently did a line following robot using P89V51RD2BN.
(All P89V51RD2 that i have, contain phillips logo)

This is how i connected the lines:

1) LM339N outputs connected to P1 (0 to 4, as i used 5 sensors).
2) P1.6 and P1.7 for PWM outputs to control the motors (using PCA)
3) P3.3 to P3.7 outputs the values it reads from the input pins.

Is it safe to connect the output pin of LM339 the uC directly?
[LM339 has open collector at outputs and uC has internal pull-ups :)]

coz, I observed one strange thing in two microcontrollers (both p89v51rd2bn).
In the first uC, P1.0 was always high, while the second one had P1.2 always low!
The problem was solved by simply replacing the microcontroller.

I'm sure that connectivity wasn't the problem. Coz multimeter beeps when i touch the uC's pin and the output pin of LM339. But I should admit that those two faulty ICs are old. And last yr, i had put it in reverse polarity once by mistake. I still remember, the microcontroller got heated up so quickly when i did that.

Could that be the cause? Or is there any other possibility?

And by the way, is there any improvements in the new pieces by NXP? or is it just the change in logo?