Frequently Asked Questions
About the use of the PTP core
Q: Loading the FPGA bitstream seems to work, but executing spec-cl or spec-vuart results in a segmentation fault. What am I doing wrong ?
A: First of all make sure you run the spec-cl or spec-vuart as root (e.g. using sudo). If you have more than one SPEC board in your computer please check the spec-sw documentation for the parameters specifying which board spec-cl and spec-vuart should use.
Q: I'm trying to run WR PTP Core on my personal FPGA boards and the MAC address for each of them is the same.
A: WR PTP Core uses the ID of digital 1-wire thermometer available on SPEC board to generate unique MAC address for each board. If you use some other board instead of SPEC there are high changes that you don't have such thermometer. Then, your MAC address is default, but you can change it manually with "mac set " wrpc shell command.
About the internals of the PTP core
Q: Why is the PLL locking the local clock to the physical link clock implemented with the help of an LM32 processor and is it not just implemented in hardware?
Three reasons:
- Because control algorithms for PLLs are not so simple
- Because HDL is difficult to debug
- Because SoftPLL takes much less space
Read the full story in the document Why the SoftPLL is not a HardPLL...