KSZ9031RNX(2012) Просмотр технического описания (PDF) - Micrel

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производитель

KSZ9031RNX
(Rev.:2012)

Gigabit Ethernet Transceiver with RGMII Support

Micrel 

Micrel, Inc.

KSZ9031RNX

During LPI mode, refresh transmissions are used to maintain the link; power savings occur in quiet periods. Approximately

every 20 to 22 milliseconds, a refresh transmission of 200 to 220 microseconds is sent to the link partner. The refresh

transmissions and quiet periods are shown in Figure 7.

Figure 7. LPI Mode (Refresh Transmissions and Quiet Periods)

Transmit Direction Control (MAC-to-PHY)

RGMII 1000Mbps transmission from MAC-to-PHY uses both rising and falling edges of the GTX_CLK clock. The

KSZ9031RNX uses the TX_EN pin as the RGMII transmit control signal (TX_CTL) to clock in the TX_EN signal on the

rising edge and the TX_ER signal on the falling edge. It also uses the TXD[3:0] pins to clock in the TX data low nibble bits

[3:0] on the rising edge and the TX data high nibble bits [7:4] on the falling edge.

The KSZ9031RNX enters LPI mode for the transmit direction when its attached EEE-compliant MAC de-asserts the

TX_EN signal (the TX_CTL pin outputs low on the rising edge), asserts the TX_ER signal (the TX_CTL pin outputs high

on the falling edge), and sets TX data bits [7:0] to 0000_0001 (TXD[3:0] pins output 0001 on the rising edge and 0000 on

the falling edge). The KSZ9031RNX remains in the 1000Mbps transmit LPI state while the MAC maintains the states of

these signals. When the MAC changes any of the TX_EN, TX_ER, or TX data signals from their LPI state values, the

KSZ9031RNX exits the LPI transmit state.

To save more power, the MAC can stop the GTX_CLK clock after the RGMII signals for the LPI state have been asserted

for 10 or more GTX_CLK clock cycles.

Figure 8 shows the LPI transition for RGMII transmit in 1000Mbps mode.

October 2012

Figure 8. LPI Transition – RGMII (1000Mbps) Transmit

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M9999-103112-1.0

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