Datasheet

DP83849IF
SNOSAX8D –JUNE 2009–REVISED APRIL 2013 www.ti.com
6.5.3 Common Flexible MII Port Configurations
Table 6-7. Common Flexible MII Port Configurations
Channel A Channel B
Mode Description
RBR[12:9] RBR[12:9]
Normal 0000 0000 MII port A assigned to Channel A,
MII Port B assigned to Channel B
Full Port Swap 0101 0101 MII port A assigned to Channel B,
MII Port B assigned to Channel A
Extender/Media Converter 1110 1110 MII RX disabled, Channel A transmits from Channel B RX data,
Channel B transmits from Channel A RX data
Broadcast TX MII Port A xx00 xx01 Both Channels transmit from TX MII Port A
Broadcast TX MII Port B xx01 xx00 Both Channels transmit from TX MII Port B
Mirror RX Channel A 10xx 11xx Channel A RX traffic appears on both Ports
Mirror RX Channel B 11xx 10xx Channel B RX traffic appears on both Ports
Disable Port A 1111 xxxx MII Port A is disabled
Disable Port B xxxx 1111 MII Port B is disabled
6.5.4 Strapped Extender or Media Converter Mode
The DP83849IF provides a simple strap option to automatically configure both channels for Extender or
Media Converter Mode with no device register configuration necessary. The EXTENDER_EN Strap can
be used in conjunction with the Auto-Negotiation Straps (AN_EN, AN0, AN1), the RMII Mode Strap, and
the Fiber Mode (FX_EN) Strap to allow many possible configurations. If Extender Mode is strapped but
RMII Mode is not, both channels will automatically be configured for Single Clock MII Receive and
Transmit Modes. The optional use of RMII Mode in conjunction with Extender Mode allows flexibility in the
system design.
Several common configurations are shown in Table 6-8.
Table 6-8. Common Strapped Extender/Media Converter Mode Configurations
Mode Auto-Negotiation Straps Fiber Mode Straps
100Mb Copper Extender Both channels are forced to 100Mb Full Duplex Disabled for both channels
100Mb Fiber Extender N/A Enabled for both channels
10Mb Copper Extender Both channels are forced to 10Mb Full Duplex Disabled for both channels
100Mb Media Converter One channel is forced to 100Mb Full Duplex Enabled for the other channel
6.5.5 Notes and Restrictions
• Extender/Media Converter: Both channels must be operating at the same speed (10 or 100Mb). This
can be accomplished using straps or channel register controls. Both channels must be in Full Duplex
mode. Both channels must either be in RMII Mode (RBR:RMII_EN = 1) or full Single Clock MII Mode
(RBR:SCMII_RX = 1 and RBR:SCMII_TX = 1) to ensure synchronous operation. If only one RX to TX
path is enabled, SCMII_RX in the RX channel (RBR register 17h bit 7) and SCMII_TX in the TX
channel (RBR register 17h bit 6) must be set to 1. Media Conversion is only supported in 100Mb
mode; one channel must be in Fiber Mode (100Base-FX) and the other channel must be in Copper
Mode (100Base-TX).
• Broadcast TX MII Port Mode: To ensure synchronous operation, both channels must be in RMII
Mode (RBR register 17h bit 5 = 1) or in Single Clock TX MII Mode (RBR register 17h bit 6 = 1). Both
channels must be operating at the same speed (10 or 100Mb). Both channels must be in Full Duplex
mode to ensure no collisions are seen. This is because in Single Clock TX MII Mode, a collision on
one PHY channel would cause both channels to send the Jam pattern.
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