lxt972a Intel Corporation, lxt972a Datasheet - Page 37

• Manufacturer Part Number: lxt972a
• Description: 3.3v Dual-speed Fast Ethernet Transceiver Datasheet
• Manufacturer: Intel Corporation

3.8.7
3.9
3.9.1
3.9.1.1
3.9.2
Datasheet
10T Polarity Correction
The LXT972A automatically detects and corrects for the condition where the receive signal (TPIP/
N) is inverted. Reversed polarity is detected if eight inverted link pulses, or four inverted end-of-
frame (EOF) markers, are received consecutively. If link pulses or data are not received by the
maximum receive time-out period (96-128 ms), the polarity state is reset to a non-inverted state.
Monitoring Operations
Monitoring Auto-Negotiation
Auto-negotiation can be monitored as follows:
Monitoring Next Page Exchange
The LXT972A offers an Alternate Next Page mode to simplify the next page exchange process.
Normally, bit 6.1 (Page Received) remains set until read. When Alternate Next Page mode is
enabled (16.1 = 1), bit 6.1 is automatically cleared whenever a new negotiation process takes place.
This prevents the user from reading an old value in 6.1 and assuming that Registers 5 and 8
(Partner Ability) contain valid information. Additionally, the LXT972A uses bit 6.5 to indicate
when the current received page is the base page. This information is useful for recognizing when
next pages must be resent due to a new negotiation process starting. Bits 6.1 and 6.5 are cleared
when read.
LED Functions
The LXT972A incorporates three direct LED drivers. On power up all the drivers are asserted for
approximately 1 second after reset de-asserts. Each LED driver can be programmed using the LED
Configuration Register (refer to
The LED drivers 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:
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Bit 17.7 is set to 1 once the Auto-Negotiation process is completed.
Bits 1.2 and 17.10 are set to 1 once the link is established.
Bits 17.14 and 17.9 can be used to determine the link operating conditions (speed and duplex).
Operating Speed
Transmit Activity
Receive Activity
Collision Condition
Link Status
Duplex Mode
If Link is down LED is off.
If Link is up LED is on.
3.3V Dual-Speed Fast Ethernet Transceiver Datasheet — LXT972A
Table 50 on page
68) to indicate one the following conditions:
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