Forum Discussion
Zarquin
Occasional Contributor
Occasional ContributorCan a 1000mbps RGMII TSE communicate with a 100mbps PC?
Dear community, is it possible to establish an Ethernet connection from Cyclone V Dev Kit to my 100Mbps LAN PC? And if so, what configuration is necessary? On the FPGA, a Triple Speed Ethernet IP M...
- Hi,
RGMII reference clocks and data rate changes with ethernet speed and has to switched in MAC. Reading negotiated speed through MI is the usual way to handle it.
FvM
Super Contributor
Super ContributorHi,
unless you force a PHY to 1GBPS only, it will autonegotiate the highest available speed with the peer, in this case 100 MBPS. There are a few cases where autonegotiation may fail, e.g. the peer advertizes 100 MBPS but the cable is too bad.
unless you force a PHY to 1GBPS only, it will autonegotiate the highest available speed with the peer, in this case 100 MBPS. There are a few cases where autonegotiation may fail, e.g. the peer advertizes 100 MBPS but the cable is too bad.
ZarquinOccasional Contributor
Occasional ContributorHi FvM,
thank you very much for the answer.
Do I have to adjust the tx_clock to the autonegotiated speed in the PHY?
More precisely: Do I have to query the speed from the corresponding Marvell PHY register and adjust the tx_clock frequency generated by the FPGA to the actual speed? Or can the tx_clock continue to operate at 125MHz ?
- FvMHi,
yes, RGMII reference clocks and data rate change according to 10/100/1000 ethernet speed. - FvMHi,
RGMII reference clocks and data rate changes with ethernet speed and has to switched in MAC. Reading negotiated speed through MI is the usual way to handle it.- Zarquin
Hello FvM,
I see.
Any idea from which Marvell 88E1111 PHY register I can read the current ethernet speed? I tried register 4_1.11:10, but that was apparently wrong. Now I am at a loss.
- FvMHi,
unfortunately I don't have 88E1111 documentation at hand. Sorry.
- Zarquin
Hi FvM,
my initial question has been answered.
I will start a new thread for the TX problem
Thanks a lot!
