DP83867CR: RGMII minimum idle per (IPG)

Richard Mourn

Part Number: DP83867CR

Ethernet defines a minimum idle period (IPG) between transmission of Ethernet packets. Gigabit Ethernet appears to allow a minimum received IPG of 8 bytes; however, in digital loopback the TI DP83867 appears to have a lower limit of 11 IPG bytes. We would like to confirm the DP83867 minimum IPG? We would also like to understand the two byte “preamble” that is required on the RGMII interface. Is the two byte preamble a part of the IPG bytes or is it in addition to the IPG?

over 5 years ago

0 Justin Lazaruk over 5 years ago

TI__Expert 7040 points

Hi Richard,

The DP83867 can support the minimum IPG of 8 bytes in analog loopback mode. The preamble is not considered to be part of the IPG. The IPG is continuous idle symbols while the preamble is "0x55".

Regards,
Justin

0 Richard Mourn over 5 years ago in reply to Justin Lazaruk

Prodigy 140 points

Thanks Justin.

We used digital loopback to confirm the minimum IPB supported. Is there is a difference in minimum IPG between digital loopback and analog loopback (since we measured 11 IPG to work in digital loopback, while 10 did not). Also please confirm that the minimum IPG in analog loopback is the same as normal operation.

Best Regards, Richard

0 Justin Lazaruk over 5 years ago in reply to Richard Mourn

TI__Expert 7040 points

Hi Richard,

The IEEE standard for IPG is 12 bytes. The DP83867 does not support a lower IPG in all modes below that. In normal operation the DP83867 will support a minimum IPG of 12 bytes and can support lower in some packets settings but because this is outside the IEEE standard not all settings can be tested.

Regards,
Justin

0 Richard Mourn over 5 years ago in reply to Justin Lazaruk

Prodigy 140 points

Thanks for clearing this up for us Justin.

Resolved!

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DP83867CR: RGMII minimum idle per (IPG)