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164 Software Developer’s Manual
Ethernet Interface
Figure 8-3. 802.3z Advertised Base Page Mapping
Table 8-2. Bits Content in TXCW.txConfigWord
The reserved bits should be written as zero. The remote fault bits [13:12] can be set by software to
indicate remote fault type to the link partner if desired. The AS and PS bits are used for
advertisement of PAUSE frame operation. Refer to clause 37 of the 802.3z specification for details.
8.6.1.4 Software Auto-Negotiation
Auto-Negotiation can also be performed by software with TXCW.ANE set to 0b. Data stored in the
txConfigWord field is transmitted during the configuration process. Software should not (in
general) read back the contents of this register.
If hardware loses receive synchronization, the contents of the TXCW register changes and during
the time of the change, the value read back can be inconsistent. In the absence of loss of
synchronization, the value read back is stable and equal to the last written value.
Software controls the negotiation process by writing the appropriate values to the
txConfigWord
and transmitting /C/ ordered sets by setting txConfig (in TXCW) to 1b. Software must monitor the
RXCW register for status of the negotiation process and respond via writes to the TXCW register
appropriately.
The software algorithm must follow the state machine implementation of sub-clause 37.3.1.5 of
IEEE 802.3z, Figure 37-6. The link timer specification is 10 ms (+10 ms/-0 ms). In some systems,
response time for the S/W implementation can make it difficult to meet this requirement if system
utilization is high due to latencies on the PCI bus.
For more information, refer to the register definitions for TXCW and RXCW in Sections 13.4.13
and 13.4.14, respectively.
Bit Description
Np
Next Page Indication
When set indicates a request for next page exchange
AS
Asymmetric Pause Connection is Desired
When set, results in independent enabling/disabling of the flow control
receive and transmit. When cleared, results in symmetric enabling/disabling
of the flow control receive and transmit
PS
Pause Function
When set, indicates that the Ethernet controller is capable and intends to
stop upon reception of 802.3x flow control Pause packets.
When cleared, indicates that the Ethernet controller is not capable, or does
not intend to stop upon reception of flow control Pause packets.
HD
Half-Duplex Ability
When set, indicates that the Ethernet controller is capable of working in
half-duplex mode of operation
FD
Full Duplex Ability
When set, indicates that the Ethernet controller is capable of working in full-
duplex mode of operation
RSV
Reserved
Should be written as 0b