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Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720/LAN8720i 41 Revision 1.0 (05-28-09)
DATASHEET
Table 5.21 Register 0 - Basic Control
ADDRESS NAME DESCRIPTION MODE DEFAULT
0.15 Reset 1 = software reset. Bit is self-clearing. For best results,
when setting this bit do not set other bits in this
register. The configuration (as described in
Section 5.3.9.2) is set from the register bit values,
and not from the mode pins.
RW/
SC
0
0.14 Loopback 1 = loopback mode,
0 = normal operation
RW 0
0.13 Speed Select 1 = 100Mbps,
0 = 10Mbps.
Ignored if Auto Negotiation is enabled (0.12 = 1).
RW Set by
MODE[2:0]
bus
0.12 Auto-
Negotiation
Enable
1 = enable auto-negotiate process
(overrides 0.13 and 0.8)
0 = disable auto-negotiate process
RW Set by
MODE[2:0]
bus
0.11 Power Down 1 = General power down mode,
0 = normal operation
RW 0
0.10 Isolate 1 = electrical isolation of transceiver from MII
0 = normal operation
RW 0
0.9 Restart Auto-
Negotiate
1 = restart auto-negotiate process
0 = normal operation. Bit is self-clearing.
RW/
SC
0
0.8 Duplex Mode 1 = Full duplex,
0 = Half duplex.
Ignored if Auto Negotiation is enabled (0.12 = 1).
RW Set by
MODE[2:0]
bus
0.7 Collision Test 1 = enable COL test,
0 = disable COL test
RW 0
0.6:0 Reserved RO 0
Table 5.22 Register 1 - Basic Status
ADDRESS NAME DESCRIPTION MODE DEFAULT
1.15 100Base-T4 1 = T4 able,
0 = no T4 ability
RO 0
1.14 100Base-TX Full
Duplex
1 = TX with full duplex,
0 = no TX full duplex ability
RO 1
1.13 100Base-TX Half
Duplex
1 = TX with half duplex,
0 = no TX half duplex ability
RO 1
1.12 10Base-T Full
Duplex
1 = 10Mbps with full duplex
0 = no 10Mbps with full duplex ability
RO 1
1.11 10Base-T Half
Duplex
1 = 10Mbps with half duplex
0 = no 10Mbps with half duplex ability
RO 1
1.10:6 Reserved
1.5 Auto-Negotiate
Complete
1 = auto-negotiate process completed
0 = auto-negotiate process not completed
RO 0