LAN9303MI-AKZE Datasheet, PDF (112/386 Pages) SMSC Corporation – Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII

Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII
Datasheet
while the link partner is the Switch Fabric. This is consistent with the intention of the Virtual
PHY.
7.3.1.1
Parallel Detection
In the event that there are no common bits between the advertised ability and the emulated link
partners ability, auto-negotiation fails and emulated parallel detect is used. In this case, the Link
Partner Auto-Negotiation Able bit of the Virtual PHY Auto-Negotiation Expansion Register
(VPHY_AN_EXP) will be cleared, and the communication set to half-duplex. The speed is determined
by the speed_strap_0 configuration strap. Only one of the technology ability bits in the Virtual PHY
Auto-Negotiation Link Partner Base Page Ability Register (VPHY_AN_LP_BASE_ABILITY) will be set,
indicating the emulated parallel detect result.
7.3.1.2
Disabling Auto-Negotiation
Auto-negotiation can be disabled in the Virtual PHY by clearing the Auto-Negotiation (VPHY_AN) bit
of the Virtual PHY Basic Control Register (VPHY_BASIC_CTRL). The Virtual PHY will then force its
speed of operation to reflect the speed (Speed Select LSB (VPHY_SPEED_SEL_LSB) bit) and duplex
(Duplex Mode (VPHY_DUPLEX) bit) of the Virtual PHY Basic Control Register (VPHY_BASIC_CTRL).
The speed and duplex bits in the Virtual PHY Basic Control Register (VPHY_BASIC_CTRL) should be
ignored when auto-negotiation is enabled.
7.3.1.3
Virtual PHY Pause Flow Control
The Virtual PHY supports pause flow control per the IEEE 802.3 specification. The Virtual PHYs
advertised pause flow control abilities are set via the Symmetric Pause and Asymmetric Pause bits of
the Virtual PHY Auto-Negotiation Advertisement Register (VPHY_AN_ADV). This allows the Virtual
PHY to advertise its flow control abilities and auto-negotiate the flow control settings with the emulated
link partner. The default values of these bits are as shown in Section 13.2.6.5, "Virtual PHY Auto-
Negotiation Advertisement Register (VPHY_AN_ADV)," on page 188.
The symmetric/asymmetric pause ability of the emulated link partner is based upon the advertised
pause flow control abilities of the Virtual PHY as indicated in the Symmetric Pause and Asymmetric
Pause bits of the Virtual PHY Auto-Negotiation Advertisement Register (VPHY_AN_ADV). Thus, the
emulated link partner always accommodates the asymmetric/symmetric pause ability settings
requested by the Virtual PHY, as shown in Table 13.6, “Emulated Link Partner Pause Flow Control
Ability Default Values,” on page 191.
The pause flow control settings may also be manually set via the Port 0 Manual Flow Control Register
(MANUAL_FC_0). This register allows the Switch Fabric Port 0 flow control settings to be manually
set when auto-negotiation is disabled or the Port 0 Full-Duplex Manual Flow Control Select
(MANUAL_FC_0) bit is set. The currently enabled duplex and flow control settings can also be
monitored via this register. The flow control values in the Virtual PHY Auto-Negotiation Advertisement
Register (VPHY_AN_ADV) are not affected by the values of the manual flow control register. Refer to
Section 6.2.3, "Flow Control Enable Logic," on page 70 for additional information.
7.3.2 Virtual PHY in MAC Mode
In the MAC mode of operation, an external PHY is connected to the MII interface of the device.
Because there is an external PHY present, the Virtual PHY is not needed for external configuration.
However, the Port 0 Switch Fabric MAC still requires the proper duplex setting. Therefore, in MAC
mode, if the Auto-Negotiation (VPHY_AN) bit of the Virtual PHY Basic Control Register
(VPHY_BASIC_CTRL) is set, the duplex is based on the P0_DUPLEX pin and duplex_pol_strap_0
configuration strap. If these signals are equal, the Port 0 Switch Fabric MAC is configured for full-
duplex, otherwise it is set for half-duplex. The P0_DUPLEX pin is typically connected to the duplex
indication of the external PHY. The duplex is not latched since the auto-negotiation process is not used.
The duplex can be manually selected by clearing the Auto-Negotiation (VPHY_AN) bit and controlling
the Duplex Mode (VPHY_DUPLEX) bit in the Virtual PHY Basic Control Register
(VPHY_BASIC_CTRL).
Revision 1.5 (07-08-11)
112
DATASHEET
SMSC LAN9303M/LAN9303Mi