Mariusz SP3FXC wrote:
I'm looking for some info on NRZI coding. google gives me useless links...
nothing special. I am about to write someting that uses NRZI but i can not
find any specification.

If you look at this with a monospaced font (Courier for example) it
should make sense:

__ ________ _____ __
__| |__| |__| |________|
0 0 0 1 1 0 0 1 0 1 1 0

Non-Return Zero Inverting means (1) the signal does not return
to a resting state after a bit, and (2) a zero is indicated by
a change of state, and a one by no change. Clock is extracted
from the data, which means there must be a limit to the number
of consecutive 1's, and the "zero stuffing" technique leads to
a bigger discussion.

HTH

NRZI encoder:

Invert the NRZ data, then apply to both the J and K inputs of a J-K
flipflop; clock to the clk input of the FF. Q output of the FF is the
encoded NRZI data.

NRZI decoder:

Encoded NRZI data to both the input of a D flipflop and one input of an
XOR gate. Q* (Q-not) output of the D-FF to the other input of the XOR gate.
Clk to the clk input of the FF. XOR output is the decoded NRZ data.


-- Tom, N5EG





"Mariusz SP3FXC" wrote in message
...
Hi,

I'm looking for some info on NRZI coding. google gives me useless
links...
nothing special. I am about to write someting that uses NRZI but i can not
find any specification.

I appreciate any input on this.

Regards,

Mariusz SP3FXC

Ok.
Thank You ALL very much for helping me. The input from You was very
helpfull.

Best regards from Poland, 73's,

Mariusz SP3FXC