
Page 154
Cortina Systems LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
LXT9785/LXT9785E
Datasheet
249241, Revision 11.0
16 April 2007
4.12 Monitoring Operations
When a long event (such as duplex status) occurs, it is edge detected and starts the
stretch timer. When the stretch timer expires, the edge detector is reset so that a long
event causes another pulse to be generated from the edge detector. The edge detector
resets the stretch timer, causing the LED driver to remain asserted.
Figure 31 onpage 154 shows how the stretch operation functions.
4.12.3
Out-of-Band Signaling
The LXT9785/LXT9785E provides an out-of-band signaling option to transfer status
information across the RMII receive interface. This feature is enabled when Register bit
25.0 = 1 and uses the RxData(1:0) data bus during the Inter-Packet Gap (IPG) time as
shown in
Figure 32. Out-of-Band signaling is disabled when Isolate mode is enabled by
setting Register 0.10.
Note:
The BGA15 package does not support Out-of-Band Signaling nor the RMII interface.
The two status bits transferred across the RxData bus are software selectable via
In normal operation, the LXT9785/LXT9785E stuffs the RxData bus with zeros during the
IPG. A software-selectable bit enables the RMII out-of-band signaling feature. Once this
bit is set, the LXT9785/LXT9785E replaces the zeros with selected status bits during the
IPG.
Figure 31
LED Pulse Stretching
Event
LED
Note: The direct drive LED outputs in this diagram are shown as active L ow.
stretch