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194 Software Developer’s Manual
PHY Functionality and Features
Table 10-2 lists the intended operation for the various settings of ASM_DIR and Pause. This
information is provided for reference only; it is the responsibility of the MAC to implement the
correct function. The PHY merely enables the two MACs to communicate their abilities to each
other.
11.9 Management Data Interface
The PHY supports the IEEE 802.3 MII Management Interface also known as the Management
Data Input/Output (MDIO) Interface. The MDIO interface consists of a physical connection to the
MAC, a specific protocol which runs across the connection, and a 16-bit MDIO register set.
PHY Registers 0d through 10d and 15d are required and their functions are specified by the IEEE
802.3 specification. Additional registers are included for expanded functionality.
11.10 Low Power Operation
The Ethernet controller can be get into a low-power state according to MAC control (Power
Management controls) or via PHY register 0d. In either power down mode, the Ethernet controller
is not capable of receiving or transmitting packets.
Table 10-2. Pause And Asymmetric Pause Settings
ASM_DIR Settings
Local
(PHY Register 4d, Bit
10) and Remote (PHY
Register 5d, Bit 10)
Pause Setting -
Local (PHY
Register 4d, Bit
9)
Pause Setting -
Remote (PHY
Register 5d, Bit
9)
Result
Both ASM_DIR = 1b
1b 1b
Symmetric - Either side can flow control
the other
1b 0b
Asymmetric - Remote can flow control
local only
0b 1b
Asymmetric - Local can flow control
remote
0b 0b No flow control
Either or both
ASM_DIR = 0b
1b 1b
Symmetric - Either side can flow control
the other
Either or both = 0b No flow control