KSZ9021RL-EVAL Board User’s Guide
Micrel, Inc.
March 20, 2009
Rev.
1.0
12/24
4.5.2 RGMII
Back-to-Back
Two KSZ9021RL-EVAL boards can be connected back-to-back via RGMII to form effectively a
Gigabit Ethernet repeater, as shown in the following figure.
Figure 3. KSZ9021RL-EVAL Board – RGMII Back-to-Back
For RGMII Back-to-Back,
•
Remove resistors [R14, R16, R136-R139] from both KSZ9021RL-EVAL boards
•
Place the two boards with their solder side facing each other, as shown above.
•
Use a 7x1 header to connect JP24 of top board to JP25 of bottom board.
•
Use a 7x1 header to connect JP25 of top board to JP24 of bottom board.
•
Use 4 sets of stand-offs, screws and nuts to fasten the two boards together, as shown
above.
Refer to KSZ9021RL Socket Board Schematic for more details on RGMII Back-to-Back.
For RGMII Back-to-Back, the two boards are powered up independently from their respective
power jack (J13), and programmed independently from their respective USB port (CN1). Both
boards need to link-up at the same speed. Ethernet traffic receive at the RJ-45 jack (RJ1) of one
board is passed to the other board via RGMII and transmitted out the RJ-45 jack (RJ1) of the
other board.
RGMII Back-to-Back is supported for 1000Base-T and 100Base-TX only. 10Base-T requires a
MAC due to preamble consumption, and therefore is not supported.
