24 Jan
2014
24 Jan
'14
3:48 p.m.
On Fri, Jan 24, 2014 at 10:14:39AM -0800, Al Kossow wrote:
Manchester-encoded transmission schemes have embedded
clocking. These go back
well before the days of the SCC. The on-wire encoding was normally hidden by
whatever modem was handling what was on the wire, so all you would see would
be clock and data.
Well, exactly. So clock insertion/recovery is the modem's business, and has
already happened by the time you get out to the computer's serial port and
are dealing with things like sync and idle characters. So I still claim
that sync/idle chars have to do with byte framing, and SDLC bit-stuffing is
for packet framing, and neither one has anything directly to do with PLL sync.
Once you establish byte framing with a couple of SYN characters, you can
send NULs all day long w/o losing your place, and they'll all be dutifully
clocked into the receiving port...
John Wilson
D Bit