Dear Team,
According to iMX7 Spec., the rise/fall time spec should not over 0.75ns.
There was too hard to meet when RGMII operation in 3.3V.
We find a document that " OPEN Alliance RGMII EPL"., the document was attached.
The shows there are operation in 3.3V, and specify maximum rise/fall time spec.is 1ns
Normaly, RGMII operation voltage is 2.5V, so rise/fall time spec. 0.75ns should not be a problem.
When RGMII operation in 3.3V, should we still follow the 0.75ns spec., or we can just make sure rise/fall time small than 1.0ns.
Please advise.
Justin.
Solved! Go to Solution.
@justin_hsieh
Hello,
i.MX7 has not been tested / specified for 3.3V ENET operations,
nevertheless following the 1.0ns spec.with 3.3V operation looks reasonable.
Regards,
Yuri.
Hi Yuri,
RGMII and GMII are similar which use the same clock - 125MHz.
RGMII often operation in 2.5V, but GMII operation in 3.3V.
RGMII speify Tr/Tf < 0.75ns.
GMII specify Tr/Tf < 1.0ns.
We know the higher voltage needs bigger rise/fall time.
So, Should we follow the 1.0ns spec.with 3.3V operation?
Please see the attachement, there is NXP LS1088A datasheet.
There shows 1.8V/2.5V, two different rise/fall time spec which are 0.75ns and 0.54ns.
I think there will be an other rise/fall time for 3.3V operation, right?
Please advise,
Tks.
@justin_hsieh
Hello,
i.MX7 has not been tested / specified for 3.3V ENET operations,
nevertheless following the 1.0ns spec.with 3.3V operation looks reasonable.
Regards,
Yuri.
Hello,
mainly it is important to consider timing budget and guarantee proper delays and setup / hold
timings for reliable operations.
https://www.ti.com/lit/an/snla243/snla243.pdf
Regards,
Yuri.