Datasheet

2.2 k:

PHYAD1 = 1PHYAD2 = 0PHYAD3 = 0PHYAD4 = 0

VCC

RXD

RXD_1

RXD

COL

PHYAD0 = 1

DP83640

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SNOSAY8E –SEPTEMBER 2007–REVISED APRIL 2013

Neither Auto-Negotiation nor Auto-MDIX is required to be enabled in forcing crossover of the MDI pairs.

Forced crossover can be achieved through the FORCE_MDIX bit, bit 14 of PHYCR (19h) register.

NOTE: Auto-MDIX will not work in a forced mode of operation.

5.4 PHY Address

The five PHY address strapping pins are shared with the RXD[3:0] pins and COL pin as shown below.

Table 5-2. PHY Address Mapping

Pin # PHYAD Function RXD Function

42 PHYAD0 COL

43 PHYAD1 RXD_3

44 PHYAD2 RXD_2

45 PHYAD3 RXD_1

46 PHYAD4 RXD_0

The DP83640 can be set to respond to any of 32 possible 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. Each

DP83640 or port sharing an MDIO bus in a system must have a unique physical address.

The DP83640 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 10.2.6 for more

information.

For further detail relating to the latch-in timing requirements of the PHY Address pins, as well as the other

hardware configuration pins, refer to the Reset summary in Section 8.

Since the PHYAD[0] pin has weak internal pull-up resistor and PHYAD[4:1] pins have weak internal pull-

down resistors, the default setting for the PHY address is 00001 (01h).

Refer to Figure 5-1 for an example of a PHYAD connection to external components. In this example, the

PHYAD strapping results in address 00011 (03h).

Figure 5-1. PHYAD Strapping Example

5.4.1 MII Isolate Mode

It is recommended that the user have a basic understanding of Clause 22 of the 802.3u standard.

The DP83640 can be put into MII Isolate Mode by writing a 1 to bit 10 of the BMCR register. Strapping the

PHY Address to 0 will force the device into Isolate Mode when powered up. 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.

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