lxt9785 Intel Corporation, lxt9785 Datasheet - Page 155

• Manufacturer Part Number: lxt9785
• Description: Advanced 8-port 10/100 Mbps Phy Transceivers
• Manufacturer: Intel Corporation

4.12
4.12.1
4.12.2
Datasheet
Document Number: 249241
Revision Number: 007
Revision Date: August 28, 2003
Note: The BGA15 package only supports two LEDs per port (LEDn_1 and LEDn_2).
Monitoring Operations
Monitoring Auto-Negotiation
Auto-negotiation may be monitored as follows:
Per-Port LED Driver Functions
The LXT9785/LXT9785E incorporates three direct drive LEDs per port (LEDn_1, LEDn_2, and
LEDn_3).
On power up, all the LEDs lights up for approximately one second after reset de-asserts. Each LED
may be programmed to one of several different display modes using the LED Configuration
Register. Each per-port LED may be programmed (refer to
(Address 20, Hex 14)” on page
The LEDs can also be programmed to display various combined status conditions. For example,
setting bits 20.15:12 = 1101 produces the following combination of Link and Activity indications:
The LED driver pins are open drain circuits (10mA max current rating). Refer to
page 167
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 is further extended (see
Table 96, “LED Configuration Register (Address 20, Hex 14)” on page
When an event such as receiving a packet occurs, it is edge detected and starts the stretch timer.
The LED driver remains asserted until the stretch timer expires. If another event occurs before the
stretch timer expires, the stretch timer is reset and the stretch time extended.
•
•
•
•
•
•
•
•
•
•
•
•
Bits 1.2 and 17.10 = 1 once the link is established.
Additional bits in Register 1 (refer to
Register 17 (refer to
be used to determine the link operating conditions and status.
Operating Speed
Transmit Activity
Receive Activity
Collision Condition
Link Status
Duplex Mode
Isolate Condition
If Link is down, LED is off.
If Link is up, LED is on.
If Link is up AND activity is detected, the LED blinks at the stretch interval selected by bits
20.3:2 and continues to blink as long as activity is present.
under the Application Information Section for LED circuit design details. The LED
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
Table 93, “Quick Status Register (Address 17, Hex 11)” on page
213) to indicate one of the following conditions:
Table 84, “Status Register (Address 1)” on page
Table 96, “LED Configuration Register
213).
“LED Circuit” on
201) and
209) can
157