Re: Link Status thoughts and other status signals
For those of us that are unfamiliar with Fibre Channel optics, could you
explain what the "Rate Select" function is?
At 04:42 PM 10/28/00 -0700, schelto.vandoorn@xxxxxxxxxxxx wrote:
>In the same sense as Rich did, I would like to throw in my 10 cents.
>Just as the link status needs to be defined, I see also the need to define
>two additional signals in the other direction. Namely transmit disable
>and rate select.
>laser transmitters are designed to always transmit light at a predefined
>average level. So even if the transmitter gets all zeroes at the input,
>after a certain amount of time it will start transmitting static light.
>From the fiber Channel the experience has been, that in some instances
>the cross talk from neighboring transmitters could be modulated onto this
>static light signal.
>The receiver on the other side has gone into maximum amplification,
>because it is not receiving a signal, and the outputs are "chattering" on
>the input noise. If the input noise, to the receiver, contains some valid
>signals, the signals might be interpreted by the upper layers as valid
>signals, and the system will oscillate between initialization and shutoff.
>To avoid this, the new transceivers have a transmit disable pin, that will
>shutoff the light coming out of the transceiver. This signal has to be
>provided by the upper layer.
>This is also a new single on transceivers and in 10 GbE will be
>optional. But I can see for some implementations that this signal could
>be useful to switch between different receive filters for different data
>rates, or different PMD's, if they are implemented.
>I strongly believe that we should also define these signals.