Using any one out of two line drivers of MAX232, I m having incorrect voltage at Rin pin (pin 13 for line driver 1 or pin 8 of line driver2).For input voltage of 5 volt at pins 9 & 10, I get -8.9v at pin 7 but in mv range at pin 8. I rechecked ckt connections & even used other IC but of no use. What could be the problem?

 

If you are sure the output is not shorted to GND. It could be a bad chip. I hvae fried some max 232 in my time

 

Your pin numbers don't match my MAX232. Can you post the part number and your circuit diagram?

 

Using any one out of two line drivers of MAX232, I m having incorrect voltage at Rin pin (pin 13 for line driver 1 or pin 8 of line driver2).For input voltage of 5 volt at pins 9 & 10, I get -8.9v at pin 7 but in mv range at pin 8. I rechecked ckt connections & even used other IC but of no use. What could be the problem?

Yes, circuit diagram please. Pin 9 is not an input. This is why you don't get anything out of pin 8. Because that's the corresponding input for pin 9.

 

ya, actually I m only transmitting from uC AT89C51 to PC & that pair input & output voltages is fine. I thnk I should be able to receive data at PC

 

Yah, post that schematic please. You seem to have some pins swapped.

Also keep in mind that the TX of your device goes to the RX of your PC, and RX of your device goes to the TX of the PC.

Seems simple but I swapped em first time I wired an SPI interface.