Changing the IFCLK source from external to internal and vice versa.

Question: When switching from internal to external IFCLK of the SX2 or FX2 device, does the external master need to do anything with the signal to prevent glitches on the IFCLK? Does the SX2 or FX2 have circuitry to ensure a smooth, glitch free transition between external and internal IFCLK?

 

Answer:

We recommend resetting the fifos immediately before and after switching the clock to ensure stable operation. There is no special clock switching mechanism that will necessarily inhibit glitches. However, generally speaking as long as there is no activity involving the fifos at the time of the switch then you should be fine. But, we recommend resetting the fifos just after to be sure.