DP83848MSQ National Semiconductor, DP83848MSQ Datasheet - Page 17

• Manufacturer Part Number: DP83848MSQ
• Manufacturer: National Semiconductor

Specifications of DP83848MSQ

• Lead Free Status / RoHS Status: Compliant

2.3 PHY Address
The 5 PHY address inputs pins are shared with the
RXD[3:0] pins and COL pin as shown below.
The DP83848M can be set to respond to any of 32 possi-
ble PHY addresses via strap pins. The information is
latched into the PHYCR register (address 19h, bits [4:0])
at device power-up and hardware reset. The PHY
Address pins are shared with the RXD and COL pins.
Each DP83848M or port sharing an MDIO bus in a system
must have a unique physical address.
The DP83848M supports PHY Address strapping values 0
(<00000>) through 31 (<11111>). Strapping PHY Address
0 puts the part into Isolate Mode. It should also be noted
that selecting PHY Address 0 via an MDIO write to
PHYCR will not put the device in Isolate Mode. See
Section 2.3.1 for more information.
For further detail relating to the latch-in timing require-
ments of the PHY Address pins, as well as the other hard-
ware configuration pins, refer to the Reset summary in
Section 6.0.
Pin #
35
36
37
38
39
Table 2. PHY Address Mapping
PHYAD Function
PHYAD0
PHYAD1
PHYAD2
PHYAD3
PHYAD4
RXD Function
Figure 2. PHYAD Strapping Example
RXD_0
RXD_1
RXD_2
RXD_3
COL
17
Since the PHYAD[0] pin has weak internal pull-up resistor
and PHYAD[4:1] pins have weak internal pull-down resis-
tors, the default setting for the PHY address is 00001
(01h).
Refer to Figure 2 for an example of a PHYAD connection
to external components. In this example, the PHYAD
strapping results in address 00011 (03h).
2.3.1 MII Isolate Mode
The DP83848M can be put into MII Isolate mode by writ-
ing to bit 10 of the BMCR register or by strapping in Phys-
ical Address 0. It should be noted that selecting Physical
Address 0 via an MDIO write to PHYCR will not put the
device in the MII isolate mode.
When in the MII isolate mode, the DP83848M does not
respond to packet data present at TXD[3:0], TX_EN inputs
and presents a high impedance on the TX_CLK, RX_CLK,
RX_DV, RX_ER, RXD[3:0], COL, and CRS outputs. When
in Isolate mode, the DP83848M will continue to respond to
all management transactions.
While in Isolate mode, the PMD output pair will not trans-
mit packet data but will continue to source 100BASE-TX
scrambled idles or 10BASE-T normal link pulses.
The DP83848M can Auto-Negotiate or parallel detect to a
specific technology depending on the receive signal at the
PMD input pair. A valid link can be established for the
receiver even when the DP83848M is in Isolate mode.
VCC
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