LXT972 Level One, LXT972 Datasheet - Page 30

• Manufacturer Part Number: LXT972
• Description: 3.3V Dual-Speed Fast Ethernet Transceiver Datasheet
• Manufacturer: Level One

LXT972 3.3V Dual-Speed Fast Ethernet Transceiver
The LED driver pins also provide initial configuration
settings. The LED pins are sensitive to polarity and will
automatically pull up or pull down to configure for either
open drain or open source circuits (10 mA Max current
rating) as required by the hardware configuration. Refer to
the discussion of
page 16
Figure 19: LED Pulse Stretching
30
LED Pulse Stretching
The LED Configuration Register also provides
optional LED pulse stretching to 30, 60, or 100 ms. If
during this pulse stretch period, the event occurs again,
the pulse stretch time will be further extended.
Event
LED
Note: The direct drive LED outputs in this diagram are shown as active Low.
for details.
stretch
“Hardware Configuration Settings” on
stretch
When an event such as receiving a packet occurs it will
be edge detected and it will start the stretch timer. The
LED driver will remain asserted until the stretch timer
expires. If another event occurs before the stretch
timer expires then the stretch timer will be reset and
the stretch time will be extended.
When a long event (such as duplex status) occurs it
will be edge detected and it will start the stretch timer.
When the stretch timer expires the edge detector will
be reset so that a long event will cause another pulse to
be generated from the edge detector which will reset
the stretch timer and cause the LED driver to remain
asserted.
functions.
Figure 19
stretch
shows how the stretch operation