Q
Can I recover a 1T clock from a EFM signal which varies between 3T and 14T?
A
The ADN2814 can recover the 1T clock from that signal. There are two ways thedevice could be configured to recover the 1T clock. The first way is the
default mode of operation where the ADN2814 automatically recovers the clock
from the incoming data stream without the need of a reference clock as an
acquisition aid. To use the device in this mode (no refclk), it is required
that the incoming signal be random in nature, with transitions at the 1T
frequency.. The signal you show in the jpeg does not have any transitions at
the 1T rate, although i am assuming that over time there would be many
transitions at the 1T rate.
If the incoming signal does not have sufficient transitions at the 1T rate,
then the ADN2814 can be configured in LTR ("Lock To Refclk") mode. In this
mode, you need to supply a reference clock that is at the desired datarate
divided by some integer "n". You can choose the "n" based on what you have
available for a reference clock. The ADN2814 can be programmed into LTR mode
via the I2C interface. This is detailed in the datasheet.