Is this rs232 waveform correct?

[ddosanjh]

I am sending the byte 0xFF to the Proteus Virtual Terminal component. Both sides are configured to 9600 baud, 2 stop, no parity.

Here is the resulting wave:


As illustrated, the pulse width in the wave form is almost exactly consistent with 9600 baud.

Here are my Virtual Terminal settings:


And here is the hex output:


Big thanks to anyone who can tell me why the wave form is not resulting in my expected '0xFF' output...

Btw, I get the same result when I send the signal through a MAX232 and invert polarity in the settings.

 

[yoramgr]

Are the waveform screenshot and hex terminal screenshot:
1. both taken from simulation, or
2. the waveform taken from simulation and terminal taken from real processor transmission?
if (2) is the case, then you need to use a scope to check the waveform.

my guess is that the transmitter somehow transmits at 4800 baud, so a receiver set to 9600 (the terminal), sees the "0" of the start bit as two bits: start bit, and the LSB of the data, which results as 0xFE.

(but maybe it's something else I didn't thing of...)

 

[FvM]

my guess is that the transmitter somehow transmits at 4800 baud

Yes. a plausible explanation. You may want to try different codes for clarification.