LXT980/980A Dual-Speed, 5-Port Fast Ethernet Repeater
32
Datasheet
internal register. The LEDs generally operate under hardware control although some limited
software overrides are available. In addition to On and Off states, some LED drivers provide a
blink state output.
2.3.1
Blink Rates
Two programmable blink rates are provided. The default period for the slow blink rate is 1.6s. The
default period is 0.4s for the fast blink rate. These rates may be changed via the LED Timer
Register. The slow blink rate is defined by the upper 8 bits and the fast blink rate is defined by the
lower 8 bits of the LED Timer Register. Refer to
Table 73
through
Table 75
for details.
2.3.2
Power-Up and Reset Conditions
During reset or power-up, all LED drivers turn on steady and remain on for approximately 2
seconds after reset is cleared. After reset, the Collision, Activity, and Redundant Power Supply
LEDs revert to hardware control. The Global Fault and Port LEDs revert to hardware control
unless a manager is present in the system.
2.3.3
Port LEDs
Port LEDs provide status for the four twisted-pair ports and the MII port. The LXT980 has 3 LED
driver pins for each port as described in
Table 8
. These pins drive standard LEDs. Three user-
selectable modes are provided for the port LEDs. Port LED states are also affected by port speed
and auto-negotiation status, see
Table 13
through
Table 15
.
2.3.3.1
Link Loss
During link loss, the Speed LED indicates10M, and the Partition LED indicates
“
No partition,
”
regardless of actual partition status.
2.3.3.2
Software Overrides of Port LEDs
The Port LED Control Register allows limited software overrides of the Port LEDs. Two bits per
port provide independent control of each port. However, all three LEDs for the respective port
receive the same override (all Port
n
LEDs will be simultaneously set to On, Off, or Blink). Refer
to
Table 69
and
Table 74
for coding and bit assignments.
2.3.4
Segment LEDs
These outputs can directly drive LEDs to indicate activity and collision status on a per segment
basis. No software overrides are provided for these LED drivers, and they are not affected by LED
mode selection. Pulse stretchers are used to extend the on-time for these LEDs.
2.3.4.1
Collision LEDs
The collision LEDs turn on for approximately 120
μ
s when the LXT980 detects a collision on the
respective 10 Mbps or 100 Mbps segment. During the time that the collision LED is on, any
additional collisions are ignored by the collision LED logic.