Intel IXF1104 - Manual (Page 126)

Intel
®
IXF1104 4-Port Gigabit Ethernet Media Access Controller
Datasheet 126
Document Number: 278757
Revision Number: 009
Revision Date: 27-Oct-2005
Note: There is a restriction when using this loopback mode. At least one clock cycle is required between
a TEOP assertion and a TSOP assertion. This is required when the pre-pend feature of the receive
FIFO is enabled to allow the addition of the extra two bytes to the data sent on the transmit
interface. Where the pre-pend feature has not been enabled, data can be sent back-to-back on the
transmit SPI3 interface with TSOP following TEOP on the next cycle.
To configure the IXF1104 MAC to use the SPI3 loopback mode, the “RX FIFO SPI3 Loopback
Enable for Ports 0 - 3 ($0x5B2)" must be configured. Each IXF1104 MAC port has a unique bit in
this register designated to control loopback. It is possible to have individual ports in a loopback
mode while other ports continue to operate in a normal mode.
5.11.2 Line Side Interface Loopback
To provide a diagnostic loopback feature on the line-side interfaces, the IXF1104 MAC can be
configured to loop back any data received by the IXF1104 MAC through one of the line interfaces
back to the corresponding transmit line interface. This is done by using the data path shown in
Figure 34 . The line-side interface can be either SerDes, RGMII or GMII. Please note that it is not
possible to loop one line-side interface back to a different one (for example, Rx SerDes looped
back to transmit RGMII).
Figure 33. SPI3 Interface Loopback Path
SPI3 Interface
Block
TX
RX
Line Side
Interface
MAC
TX FIFO
RX FIFO
B3229-01
SPI3 Internal Loopback