Texas Instruments DP83561EVM, User Manual, Page: 16 / 60

4 BER Testing
The DP83561EVM supports BER testing through RGMII back-to-back configuration and/or internal loopback
modes.
RGMII BER Testing - Back-to-Back Configuration
The DP83561EVM supports RGMII BER testing through back-to-back configuration as described by RGMII
Back-to-Back Configuration . BER testing can be conducted using two DP83561EVMs and two link partners by
checking the packets sent and received by the two link partners.
Referring to Figure 3-3 , should a second link partner, Link Partner B, be unavailable, DP83561EVM B can be
programmed into Analog Loopback for the BER test. In this case, Link Partner A will send data across the cable
to DP83561EVM A, to be sent across the RGMII interface to DP83561EVM B, looped back to DP83561EVM A,
and received by Link Partner A. Please note, that in Analog Loopback, the MDI output pairs must have a 100
ohm differential termination. The RGMII Transmit Clock Delay must be set such that the RGMII transmit clock is
aligned with respect to transmit data for both boards. This can be done with the following register write:
• Write Register 0x32 = 0xD2
For additional information on configuring loopback modes, please refer to the device data sheet.
RGMII BER Testing - External Loopback Configuration
The DP83561EVM support RGMII BER testing through an external loopback configuration using the MAC
Interface Breakout Board. The MAC Interface Breakout Board may be connected to the main DP83561EVM
board as described in
MAC Interface Breakout Board Configuration . To configure the MAC Interface Breakout
Board for external loopback, jumpers must be placed to connect the transmit pins to the corresponding receive
pins. Refer to
Figure 4-1 for a connection diagram. The RGMII Transmit Clock Delay must be set such that the
RGMII transmit clock is aligned with respect to transmit data. This can be done with the following register write:
• Write Register 0x32 = 0xD2
MAC Interface
Breakout Board
TXD3
TXD2
TXD1
TXD0
TXCTRL
GTXCLK
RXD3
RXD2
RXD1
RXD0
RXCTRL
RXCLK
RXER
MDIO
MDC
RESET
CRS
COL
Figure 4-1. MAC Interface Breakout Board External Loopback Connection Diagram
MII BER Testing
In MII mode, the MAC Interface Breakout Board may be used as described in MAC Interface Breakout Board
Configuration to support MII BER testing. Referring to Figure 4-2 , the link partner, which can be another
DP83561EVM, must be configured for Reverse Loopback, and the MII MAC must be configured to generate and
BER Testing www.ti.com
16 DP83561EVM User’s Guide SLVUC11 – APRIL 2021
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