Yes, any asychronous serial data uses start and stop bits and the idea has been in use since the 60's. It is usually used where RS232 is involved. It is also used in MIDI. The actual voltages and currents differ widely between systems. The standard format is: start bit, a number of data bits (usually 8) starting with the LSB and finishing with the MSB, then the stop bit. If more data is to be sent then the new start bit can be sent immediately after the stop bit. A start bit can occur at any time following the stop bit time cell however. Obviously each bit occupies the same time interval or cell. The number of time cells per second is the baud rate.

As far as the polarity is concerned any bit which causes a voltage that is different to the resting voltage of the signal is called a 'mark'. The start bit is a mark as are the '0's. The stop bit and the '1's are the same as the resting voltage of the serial signal. This can be a bit confusing as one might expect the signal to rest at the '0' level but this is not the case.

The receiver's sampling clock is reset at the start of every start bit so a slight baud rate disagrrement between transmitter and receiver is not serious. However, a larger error will eventually cause wrong bits to be sampled in the receiver. This happens first to the later bits in the word (MSBs) because more time has elapsed to allow a sampling time error to build up.

I would advise the pseron with the problem to try raising the receiver baud rate slightly. If this is a PIC then the SPBRG value needs to come down a touch (not up).

John R