Datasheet

16-bit Non-PCI Small Form Factor 10/100 Ethernet Controller with Variable Voltage I/O & HP Auto-MDIX Support
Datasheet
SMSC LAN9220 75 Revision 2.9 (03-01-12)
DATASHEET
full-duplex transmission. Therefore, these signals cannot be used as a verification method of
transmitted packets when transmitting in 10/100 Mbps full-duplex modes.
Note 4.1 The LAN9220 10/100 PHY internal CRS signal operates in two modes: Active and Low.
When in Active mode, the internal CRS will transition high and low upon line activity, where
a high value indicates a carrier has been detected. In Low mode, the internal CRS stays
low and does not indicate carrier detection. The internal CRS signal and No Carrier (bit 10
of the TX Status word) cannot be used as a verification method of transmitted packets
when transmitting in 10/100 Mbps full-duplex mode.
4.8 HP Auto-MDIX
HP Auto-MDIX facilitates the use of CAT-3 (10 Base-T) or CAT-5 (100 Base-T) media UTP interconnect
cable without consideration of interface wiring scheme. If a user plugs in either a direct connect LAN
cable, or a cross-over patch cable, as shown in Figure 4.3, the SMSC LAN9220 Auto-MDIX PHY is
capable of configuring the TPO and TPI twisted pair pins for correct transceiver operation.
The internal logic of the device detects the TX and RX pins of the connecting device. Since the RX
and TX line pairs are interchangeable, special PCB design considerations are needed to accommodate
the symmetrical magnetics and termination of an Auto-MDIX design.
The Auto-MDIX function can be disabled through an internal register 27.15, or the external control pins
AMDIX_EN. When disabled the TX and RX pins can be configured with the Channel Select
(CH_SELECT) pin as desired.
Table 4.2 CRS Behavior
MODE SPEED DUPLEX ACTIVITY
CRS BEHAVIOR
(Note 4.1)
Manual 10 Mbps Half-Duplex Transmitting Active
Manual 10 Mbps Half-Duplex Receiving Active
Manual 10 Mbps Full-Duplex Transmitting Low
Manual 10 Mbps Full-Duplex Receiving Active
Manual 100 Mbps Half-Duplex Transmitting Active
Manual 100 Mbps Half-Duplex Receiving Active
Manual 100 Mbps Full-Duplex Transmitting Low
Manual 100 Mbps Full-Duplex Receiving Active
Auto-Negotiation 10 Mbps Half-Duplex Transmitting Active
Auto-Negotiation 10 Mbps Half-Duplex Receiving Active
Auto-Negotiation 10 Mbps Full-Duplex Transmitting Low
Auto-Negotiation 10 Mbps Full-Duplex Receiving Active
Auto-Negotiation 100 Mbps Half-Duplex Transmitting Active
Auto-Negotiation 100 Mbps Half-Duplex Receiving Active
Auto-Negotiation 100 Mbps Full-Duplex Transmitting Low
Auto-Negotiation 100 Mbps Full-Duplex Receiving Active