Sun Microsystems THE SUN 805-7945-10 - Manual (Page 10)

6 Platform Notes: The Sun GigabitEthernet Device Driver • March 1999
Defining the Current Status
The read-only parameters described in TABLE 2 explain the operational mode of the
interface. Based on the value of these parameters, you can determine the current
status of a link.
Flow Control Parameters
The GEM ASIC is capable of sourcing (transmitting) and terminating (receiving)
pause frames conforming to IEEE 802.3x Frame Based Link Level Flow Control
Protocol. In response to received flow control frames, the GEM can slow down its
transmit rate. On the other hand, GEM is capable of sourcing flow control frames,
requesting the link partner to slow down, provided that the link partner supports
this feature. By default, GEM advertises Receive PAUSE capability during
autonegotiation.
For normal operations, GEM doesn’t need to source flow control frames. However, if
GEM is operating on a slow bus (for instance, a 33-MHz PCI bus slot), and there is a
lot of frame reception activity, there could be a performance degradation due to
Receive FIFO overflow. If the link partner is capable of terminating PAUSE flow
control frames, the performance of GEM could be improved by enabling
adv_pauseTX and restarting autonegotiation.
TABLE 2 Read-Only Parameters Defining the Current Status
Parameter Values and Description
link_status Current link status
0 = Link down
1 = Link up
link_speed Valid only if the link is up
0 = Link is not up
1000 = 1000 Mbps
link_mode Valid only if the link is up
0 = Half duplex
1 = Full duplex
TABLE 3 Read-Write Flow Control Parameters Values and Descriptions
Parameter Values
(on/off) Description
adv_pauseTX 0, 1 Transmit PAUSE Capable (default: not capable)
adv_pauseRX 0, 1 Receive PAUSE Capable (default: capable)