Micrel, Inc.

KS8721BL/SL

June 2009

10

M9999-062509-1.3

Strapping Options

(1)

Pin Number

Pin Name

Type

(2)

Pin Function

6, 5,

4, 3

PHYAD[4:1]/

RXD[0:3]

Ipd/O

25

PHYAD0/

INT#

Ipu/O

PHY Address latched at power-up/reset. The default PHY address is 00001.

9

(3)

PCS_LPBK/

RXDV

Ipd/O

Enables PCS_LPBK mode at power-up/reset. PD (default) = Disable, PU = Enable.

11

(3)

ISO/RXER

Ipd/O

Enables ISOLATE mode at power-up/reset. PD (default) = Disable, PU = Enable.

21

(3)

RMII/COL

Ipd/O

Enables RMII mode at power-up/reset. PD (default) = Disable, PU = Enable.

22

(3)

RMII_BTB

CRS

Ipd/O

Enable RMII back-to-back mode at power-up/reset. PD (default) = Disable,

PU = Enable.

27

SPD100/

No FEF/

Ipu/O

Latched into Register 0h bit 13 during power-up/reset. PD = 10Mbps, PU (default) =

100Mbps. If SPD100 is asserted during power-up/reset, this pin is also latched as

LED1 the Speed Support in register 4h. (If FXEN is pulled up, the latched value 0

means no Far_End _Fault.)

28

DUPLEX/

LED2

Ipu/O

Latched into Register 0h bit 8 during power-up/reset. PD = Half-duplex, PU (default) =

Full-duplex. If Duplex is pulled up during reset, this pin is also latched as the Duplex

support in register 4h.

29

NWAYEN/

LED3

Ipu/O

Nway (auto-negotiation) Enable. Latched into Register 0h bit 12 during power-up/reset.

PD = Disable Auto-Negotiation, PU (default) = Enable Auto-Negotiation.

30

PD#

Ipu

Power-Down Enable. PU (default) = Normal operation, PD = Power-Down mode.

Notes:

1.

Strap-in is latched during power-up or reset.

2.

Ipu = Input with internal pull-up.

Ipd/O = Input with internal pull-down during reset; output pin otherwise.

Ipu/O = Input with internal pull-up during reset; output pin otherwise.

See “Reference Circuit” section for pull-up/pull-down and float information.

3.

Some devices may drive MII pins that are designated as output (PHY) on power-up, resulting in incorrect strapping values latched at reset.

It is recommended that an external pull-down via 1kΩ resistor be used in these applications to augment the 8721’s internal pull-down.