MODBUS start, stop bits with USART

Guest · Posted: Mon May 22, 2006 4:38 pm

I see from the forum that modbus is nothing new on the PIC (it is for me, I'm a late-bloomer). I've read a few comments about parity and how it must be handled in software, but nothing regarding start/stop bits.

The modbus spec says every RTU byte transferred is 11 bits: 1 start + 8 data + 1 parity (or extra stop) + 1 stop. It seems like the example code I've seen here doesn't account for the start/stop bits. How and where are they handled?

Thanks!
-peter

Guest · Posted: Mon May 22, 2006 4:54 pm

They are handled in hardware. The USART takes care of them.

pheinrich · Joined: 22 May 2006 Posts: 1 Location: Seattle, WA

Thanks, that's what I wanted to hear!