Yogesh rathore wrote:
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Hello folks !

Can we directly connect T89C51rd2 ports (I/Os) to real world devices?

That depends what "real world devices" are... If you are talking about other CMOS chips then yes. If you are talking about low-current LEDs then yes (connect the cathode to the port pin). Remember that the 8051 port pins can source almost no current (less than 0.1mA) and can sink 5-20mA depending on the device - check the datasheet.

If yes, which pins are to be used for IN and OUT.

All pins can be used for both purposes.

Best regards,

Mikkel C. Simonsen