Im trying to look at some 422 differential pulses on a scope.
running t 115200 buad rate.

I am doing the math in the scope so i can see the diff signal of A-B essentially.
I am trying to understand what the pulse width of each logic one or zero should be so i can decipher what is being output on the scope.

How can i calculate the pulse width of a logic bit?

obviously 1/115200 is ~8uS per bit but I'm not sure that really means the pulse width of that bit is truly 8uS.

Any thoughts on how to assume the pulse width?
Thanks

 

obviously 1/115200 is ~8uS per bit but I'm not sure that really means the pulse width of that bit is truly 8uS.

It is. Simple as that.

 

Ok, i must have another problem them because im seeing 500nS pulse width running at 115200 baud

 

Ok, i must have another problem them because im seeing 500nS pulse width running at 115200 baud

Yes. There should be no 500ns pulses on a 115200 baud datastream. If it is RS422 then there is a slight possibility of an odd pulses when the driver is enabled and disabled.

 

Yes. There should be no 500ns pulses on a 115200 baud datastream. If it is RS422 then there is a slight possibility of an odd pulses when the driver is enabled and disabled.

Can you explain a bit more. I am seeing a a start bit that is about 25% of the pulse width of the other bits and them what appears to be a random logic zero bit before the 8 bit LSB starts in little endian order.

Any ideas?

 

each byte is framed by a start bit (space) and a stop bit (mark). Is that what you are seeing?

Space=0
Mark=1
but on RS232 everything is inverted.
on RS422 you get both inverted and non-inverted signals.