lxt972a Intel Corporation, lxt972a Datasheet - Page 28

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

LXT972A — 3.3V Dual-Speed Fast Ethernet Transceiver Datasheet
3.6.7
3.6.7.1
3.6.7.2
28
100Mbps
10Mbps
1. Test Loopback is enabled when 0.14 = 1
Speed
Figure 12. Loopback Paths
Table 9.
Full-Duplex
Half-Duplex
Full-Duplex
Half-Duplex, 16.8 = 0
Half-Duplex, 16.8 = 1
Loopback
The LXT972A provides two loopback functions, operational and test (see
paths are shown in
Operational Loopback
Operational loopback is provided for 10Mbps half-duplex links when bit 16.8 = 0. Data transmitted
by the MAC (TXData) is looped back on the receive side of the MII (RXData). Operational
loopback is not provided for 100Mbps links, full-duplex links, or when 16.8 = 1.
Test Loopback
A test loopback function is provided for diagnostic testing of the LXT972A. During test loopback,
the twisted-pair interface is disabled. Data transmitted by the MAC is internally looped back by the
LXT972A and returned to the MAC.
Test loopback is available for both 100TX and 10T operation. Test loopback is enabled by setting
bits as follows:
Carrier Sense, Loopback, and Collision Conditions
Duplex Condition
•
•
•
0.8 = 1 (full-duplex)
0.12 = 0 (disable auto-negotiation).
0.14 = 1
LXT972A
MII
Loopback
10T
Figure
Digital
Block
Transmit or Receive
Transmit or Receive
Transmit or Receive
Carrier Sense
12.
Receive Only
Receive Only
Loopback
100X
Analog
Block
Loopback
TX Driver
Test
Yes
Yes
Yes
No
No
1
Operational
Loopback
Yes
No
No
No
No
Table
Transmit and Receive
Transmit and Receive
Transmit and Receive
9). Loopback
Collision
None
None
Datasheet