I'm working with some RS232,485 and 422 transceiver chips (MAX232e, MAX13448e and MAX13487e) and am experiencing unexpected behavior.
Based on prior experience with using MAX232 chips with a micro, I was expecting the RX line (receiver output) on the chips to be active high (idle low)....and since they are fail-safed I was expecting that if I powered them up with no connection, they would idle low, but instead they are all holding the receiver output pin high.
I went back and studied the data sheets and this is apparently the proper behavior.
So now I'm confused. Are these inverting drivers (active low)? If that's the case, why have I never had to invert the output to communicate with a micro?
Based on prior experience with using MAX232 chips with a micro, I was expecting the RX line (receiver output) on the chips to be active high (idle low)....and since they are fail-safed I was expecting that if I powered them up with no connection, they would idle low, but instead they are all holding the receiver output pin high.
I went back and studied the data sheets and this is apparently the proper behavior.
So now I'm confused. Are these inverting drivers (active low)? If that's the case, why have I never had to invert the output to communicate with a micro?