LAN8808D datasheet(21/80 Pages) MICROCHIP

21 / 80 page

LAN8808D

DS00005833C-page 21

3.3

Configuration Straps

Configuration straps allow various features of the device to be automatically configured to user defined values. Config-

uration straps are latched upon the release of pin reset (RESET_N). Configuration straps do not include internal resis-

tors and require the use of external resistors.

3.3.1

DEVICE MODE SELECT (MODE_SEL[4:0])

The MODE_SEL[4:0] configuration straps select the device mode as follows:

Note:

The system designer must ensure that configuration strap pins meet timing requirements. If configuration

strap pins are not at the correct voltage level prior to being latched, the device may capture incorrect strap

values.

Note:

When externally pulling configuration straps high, the strap must be tied to VDDIO.

APPLICATION NOTE: All straps must be pulled-up or pulled-down externally on the PCB to enable the desired

operational state.

Note:

1000BT Half Duplex is not advertised in any of the below device modes.

Note:

When no strap-based configured is wanted, it is recommended to set MODE_SEL[4:0] to either 0x18

(single-port system) or 0x19 (multi-port system). Both values enable 1000FD 100FD/HD 10FD/HD with

EEE.

TABLE 3-9:

DEVICE MODE SELECTIONS

Test Modes

MODE_

SEL

[4:0]

Mode

00010 RESERVED

00011 RESERVED

00100 RESERVED

00101 RESERVED

00110 RESERVED

00111 RESERVED

Functional Modes

Power Down

01000 Software Power Down PLL Enabled

01001 RESERVED

Auto-Negotiation Disabled, Auto MDIX Disabled, EEE Disabled

01010 1000FD Master

01011 100FD

01100 100HD

Legend:

1000FD = 1000BASE-T Full Duplex

100FD = 100BASE-TX Full Duplex

100HD = 100BASE-TX Half Duplex

10FD = 10BASE-T Full Duplex

10HD = 10BASE-T Half Duplex

“X” means “is advertised by auto-negotiation” (for example 10BT FD and 10BT HD are both available auto-negotiation

results when MODE_SEL = 10000).

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