Thanks every body specially Mr. Mahmood,

I fully agree with your opinion about the input/outputs of Microcontroller. But my question is whether we can use the assembly language to create the internal relay features as it is done in relay ladder logic programming ? I think that was the reason plcs became very popular in industrial automation. It reduced the bulky relays in the starter boxes.

8051 derivatives with Flash memory of 64KB has posed a challenge to the expensive plcs for small automation controls except the internal relays.

Your comments about the internal relays will be highly appreciated.

Regards

Rashu