High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
Chapter 7 Ethernet PHYs
7.1
Functional Overview
The LAN9312 contains three PHYs: Port 1 PHY, Port 2 PHY and a Virtual PHY. The Port 1 & 2 PHYs
are identical in functionality and each connect their corresponding Ethernet signal pins to the switch
fabric MAC of their respective port. These PHYs interface with their respective MAC via an internal MII
interface. The Virtual PHY provides the virtual functionality of a PHY and allows connection of the Host
MAC to port 0 of the switch fabric as if it was connected to a single port PHY. All PHYs comply with
the IEEE 802.3 Physical Layer for Twisted Pair Ethernet and can be configured for full/half duplex 100
Mbps (100BASE-TX) or 10Mbps (10BASE-T) Ethernet operation. All PHY registers follow the IEEE
802.3 (clause 22.2.4) specified MII management register set and can be configured indirectly via the
Host MAC, or directly via the memory mapped Virtual PHY registers. Refer to Section 14.4, "Ethernet
PHY Control and Status Registers" for details on the Ethernet PHY registers.
The LAN9312 Ethernet PHYs are discussed in detail in the following sections:
Section 7.2, "Port 1 & 2 PHYs," on page 83
Section 7.3, "Virtual PHY," on page 96
7.1.1
PHY Addressing
Each individual PHY is assigned a unique default PHY address via the phy_addr_sel_strap
configuration strap as shown in Table 7.1. In addition, the Port 1 PHY and Port 2 PHY addresses can
be changed via the PHY Address (PHYADD) field in the Port x PHY Special Modes Register
(PHY_SPECIAL_MODES_x). For proper operation, all LAN9312 PHY addresses must be unique. No
check is performed to assure each PHY is set to a different address. Configuration strap values are
latched upon the de-assertion of a chip-level reset as described in Section 4.2.4, "Configuration
Straps," on page 40.
Table 7.1 Default PHY Serial MII Addressing
VIRTUAL PHY DEFAULT
ADDRESS VALUE
PORT 1 PHY DEFAULT PORT 2 PHY DEFAULT
PHY_ADDR_SEL_STRAP
ADDRESS VALUE
ADDRESS VALUE
0
1
0
1
1
2
2
3
Revision 1.2 (04-08-08)
SMSC LAN9312
DATA8S2HEET
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