LAN8700 Datasheet, PDF (46/74 Pages) SMSC Corporation – ±15kV ESD Protected MII/RMII Fast-Ethernet PHY with HP Auto-MDIX and SMSC flexPWR TM in a Small Footprint

LAN8700/LAN8700i
FIGURE 5-4:
CONNECTOR LOOPBACK BLOCK DIAGRAM
10/100
Ethernet
MAC
TXD
RXD
Digital
Analog
Ethernet Transceiver
1
TX
2
3
XFMR
RX
4
5
6
7
8
RJ45 Loopback Cable.
Created by connecting pin 1 to pin 3
and connecting pin 2 to pin 6.
5.4.9 CONFIGURATION SIGNALS
The PHY has 11 configuration signals whose inputs should be driven continuously, either by external logic or external
pull-up/pull-down resistors.
5.4.9.1 Physical Address Bus - PHYAD[4:0]
The PHYAD[4:0] signals are driven high or low to give each PHY a unique address. This address is latched into an inter-
nal register at end of hardware reset. In a multi-PHY application (such as a repeater), the controller is able to manage
each PHY via the unique address. Each PHY checks each management data frame for a matching address in the rel-
evant bits. When a match is recognized, the PHY responds to that particular frame. The PHY address is also used to
seed the scrambler. In a multi-PHY application, this ensures that the scramblers are out of synchronization and dis-
perses the electromagnetic radiation across the frequency spectrum.
5.4.9.2 Mode Bus – MODE[2:0]
The MODE[2:0] bus controls the configuration of the 10/100 digital block. When the nRST pin is deasserted, the register
bit values are loaded according to the MODE[2:0] pins. The 10/100 digital block is then configured by the register bit
values. When a soft reset occurs (bit 0.15) as described in Table 5-30, the configuration of the 10/100 digital block is
controlled by the register bit values, and the MODE[2:0] pins have no affect.
TABLE 5-48: MODE[2:0] BUS
Default Register Bit Values
Mode [2:0]
Mode Definitions
Register 0
Register 4
[13,12,10,8]
000
10Base-T Half Duplex. Auto-negotiation disabled.
001
10Base-T Full Duplex. Auto-negotiation disabled.
010
100Base-TX Half Duplex. Auto-negotiation disabled.
CRS is active during Transmit & Receive.
011
100Base-TX Full Duplex. Auto-negotiation disabled.
CRS is active during Receive.
100
100Base-TX Half Duplex is advertised. Auto-
negotiation enabled.
CRS is active during Transmit & Receive.
101
Repeater mode. Auto-negotiation enabled. 100Base-
TX Half Duplex is advertised.
CRS is active during Receive.
0000
0001
1000
1001
1100
1100
[8,7,6,5]
N/A
N/A
N/A
N/A
0100
0100
DS00002260A-page 46
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