Kobayashi-san,
The reference clock to the PLL ( called GTX_CLK on the TLK1501) must be present for the device to operate, even if the device is being used only for the receiver portion. There is one PLL in the SERDES device, and this PLL supports both the transmit and receive functions. The receiver takes the high speed internal clock phases from the PLL and the Clock/Data Recovery (CDR) function uses these clock phases to align a new clock phase to the center of the incoming data eye to make the recovered bit clock. Therefore, GTX_CLK is needed in order for the device RX to function. Without GTX_CLK the RX data will not be recovered.
-Atul
From: Kobayashi,
Masanori
Subject: question about TLK1501 clock recovery circuit
Atul,
I have the question about the clock recovery circuit of TLK1501. What happens in TLK1501 RX if the RX data would be input without GTX_CLK? As I see the datasheet, the GTX_CLK is the clock for TX but the GTX_CLK is input to the block of interpolator and clock recovery from the internal clock synthesizer, as a bit clock. Could you let me know the behavior of clock recovery in detail?
Regards,
Masanori Kobayashi