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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 MAC is connected via RGMII to the Marvell 88E1111 PHY on the board.
I have configured the MAC and PHY registers.
MAC Cmd Config: 0x2033 (SW Reset, Pad en, RX en, TX en)
Marvell Ctrl Reg: 0x9140 (SW Reset, 1000 Mbps, Full Duplex)
Do I need to explicitly configure the Marvell Ctrl Register to 100Mbps to establish a 100Mbps connection to my PC or does the PHY do this automatically?
The Marvell has the hardware configuration:
config 0, config 1, config 3 = 000 (PHY Address = 00000, Disable 125MHz clock)
config 2, config 5 = 111 (ANEG =1110 = Auto-Neg, advertise all capabilities, prefer Master)
config 4 = 011 (HWCFG = 1011 = RGMII to copper)
config 6 = 010
- 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.
9 Replies
FvMSuper Contributor
Hi,
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.
ZarquinHi 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.
paveetirrasrie_AlteraFrequent Contributor
Hi,
I’m glad that your question has been addressed, I now transition this thread to community support.
If you have a new question, feel free to open a new thread to get the support from Intel experts.
Otherwise, the community users will continue to help you on this thread.
Thank you.
