KSZ9021RL-EVAL Board User’s Guide
Micrel, Inc.
March 20, 2009
Rev.
1.0
11/24
4.5 Reduced Gigabit Media Independent Interface (RGMII)
The KSZ9021RL-EVAL board provides open access to the KSZ9021RL device’s RGMII signals,
and enables the RGMII signals to be wired for the following three usages:
•
RGMII Loop Back
•
RGMII
Back-to-Back
•
RGMII Connection to GMAC
4.5.1 RGMII
Loop
Back
The KSZ9021RL-EVAL board is shipped with the RGMII signals configured for RGMII Loop Back.
Resistors [R14, R16, R136-R139] are populated to connect the RGMII output clock and signals to
their respective RGMII input clock and signals. Refer to KSZ9021RL Socket Board Schematic for
details.
RGMII Loop Back enables the KSZ9021RL device to operate as a standalone evaluation platform
without the need of an external GMAC. Ethernet traffic from the link partner (Spirent SmartBits
6000B in the following figure) are received by the KSZ9021RL device, looped back externally via
RGMII pins, and transmitted back to the link partner.
Figure 2. KSZ9021RL-EVAL Board – RGMII Loop Back
RGMII Loop Back is supported for 1000Base-T and 100Base-TX only. 10Base-T requires a MAC
due to preamble consumption, and therefore is not supported.
