What do all the different parity options mean?

[Robert Claeson]

In article <4090 at amelia.nas.nasa.gov>, izen at amelia.nas.nasa.gov (Steven H. Izen) writes:

: I know what even parity and odd parity are, but what does *space* or
: *mark* mean in a parity choice?

Space = parity always cleared.
Mark  = parity always set.

: Also, I think I understand what happens when the bits/parity is 8/none
: or 7/even or 7/odd.  But where is the parity bit stored when 8/even is
: used?

Yes. The parity bit is *not* part of the data sent, but of the *protocol*
used to send the data. Therefore, parities and such have more to do with
start and stop bits than with the data bits. Any reasonable tty driver
should strip off all *protocol* information (including software flow control)
and only pass you the interesting stuff, ie the data without any parity.

So, 7 data bits and even parity is really sent as <start bit> <7 data bits>
<parity bit> <stop bit>. Some weird protocols uses two or even one-and-a-half
stop bit. Therefore, 8 data bits and even parity is sent as <start bit>
<8 data bits> <parity bit> <stop bit>. Nothing strange about it.

: Is there any good introductory reference to this?

Not as far as I know, but I'd like to see one.

-- 
          Robert Claeson      E-mail: rclaeson at erbe.se
	  ERBE DATA AB