We are using the AM3358 CZC package, Beagle Bone Black, and using its RGMII MAC to interface with a Gigabit PHY from Micrel KSZ9031RNX. We had set up the AM3358 to be clock master for TXCLK (ball K18). The copper side of the Micrel PHy goes to a Marvell Ethernet switch CU interface.
We can see from using the Marvell debug tool that we are getting about a 0.5% packet errors.
Our first suspicion is the TXCLK (ball K18) from the Beagle Bone Black because we can see a lot of jitter. It’s about 10-20% of the clock period. We are using 24Mhz input crystal, 18pF fundamental mode.
So our questions are:
- Is the jitter we are seeing normal?
- If not, what should we be investigating to alleviate the jitter?
