Method and circuitry for de-skewing data in data communication networks
such as a SONET. The data is sent from a system chip to a framer chip
where the data is de-skewed. To detect data skew, the system chip sends a
training sequence to the framer chip. The information bits sent to the
framer chip are searched in order to detect the training sequence. The
training sequences contain clear transition patterns at which all 16 bits
of the transmit data and the TCTL signal line are inverted. If any bit
does not invert, this bit must be a skewed bit. Based on the data one
clock cycle before and one clock cycle after this transition, the skewed
bit can be corrected back. After the data skew is detected, a
multiplexing logic circuitry is used to correct the skew based on one
clock cycle either before or after the transition. The multiplexing logic
circuitry includes at least three registers coupled to the inputs of the
multiplexing logic circuitry.