Part Number: AM5718
I am using the AM5718AABCX in a design and I have a question about the RGMII. I completed the PCB layout and closely matched the RGMII TX and RX lines using delay timing value in Altium. The numbers are listed:
| To Resistor | After | Total Delay in pS | ||
| ETH_TXCLK | 24.57 | 455.772 | 480.342 | |
| ETH_TXCTRL | 20.051 | 459.727 | 479.778 | |
| ETH_TXD3 | 20.055 | 459.916 | 479.971 | |
| ETH_TXD2 | 20.548 | 460.141 | 480.689 | |
| ETH_TXD1 | 15.479 | 464.644 | 480.123 | |
| ETH_TXD0 | 25.318 | 455.064 | 480.382 | |
| ETH_RXCLK | 8.843 | 416 | 424.843 | |
| ETH_RXCTRL | 24.294 | 400.483 | 424.777 | |
| ETH_RXD3 | 8.843 | 416.107 | 424.95 | |
| ETH_RXD2 | 8.843 | 416.277 | 425.12 | |
| ETH_RXD1 | 8.843 | 416.125 | 424.968 | |
| ETH_RXD0 | 8.843 | 416.085 | 424.928 |
I was expecting close timing from the phy, however there is a delay necessary from the Ethernet Phy to get higher transfer speeds.
| Rx Delay | Tx Delay | Link works? | Tx rate | Rx rate |
| 2.25ns | 0.25ns | Yes (default) | 750Mbit/s | 708Mbit/s |
| 2.25ns | 1.5ns | Yes | 660Mbit/s | 665Mbit/s |
| 2.25ns | 1.75ns | No | N/A | N/A |
| 2.25ns | 2.00ns | No | N/A | N/A |
| 2.00ns | 1.5ns | Yes | 700Mbit/s | 707Mbit/s |
Is the AM518 RMGII compatible with Version 2.0 of the RGMII Specification? Which says that no PCB trace delay is necessary. If not am I required to add in delays in the PCB traces on the RGMII lines for the AM5718?
