DP83821 datasheet(7/86 Pages) NSC

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2.0 Pin Descriptions (Continued)

Clock Interface

Symbol

Pin No(s)

Direction

Description

122

Crystal/Oscillator Input: This pin is the primary clock reference input for the

DP83821 IC and must be connected to a 25MHz 0.005% (50ppm) clock source.

The DP83821 device supports either an external crystal resonator connected

across pins X1 and X2, or an external CMOS-level oscillator source connected

to pin X1 only.

121

Crystal Output: This pin is used in conjunction with the X1 pin to connect to an

external 25MHz crystal resonator device. This pin must be left unconnected if

an external CMOS oscillator clock source is utilized. For more information see

the definition for pin X1.

Phy And General Purpose Interface

Symbol

Pin No(s)

Direction

Description

GP1DUP

131

I/O

General Purpose Pin 1 or Duplex Status: By default, this pin can be used to

input the Full Duplex status from an external Phy. The pin can also be

programmed as a general purpose I/O. This pin pad has an internal weak pull

up.

GP2

127

I/O

General Purpose Pin 2: This pin is a general purpose I/O pin that can be

programmed as an input or output. This pin has an internal weak pull up.

GP3

128

I/O

General Purpose Pin 3: This pin is a general purpose I/O pin that can be

programmed as an input or output. This pin has an internal weak pull up.

GP4

129

I/O

General Purpose Pin 4: This pin is a general purpose I/O pin that can be

programmed as an input or output. This pin has an internal weak pull up.

GP5

130

I/O

General Purpose Pin 5: This pin is a general purpose I/O pin that can be

programmed as an input or output. This pin has an internal weak pull up.

PHYLNK

132

Phy Link Status: This can be used to input the Phy Link Status. This allows the

value to be read back from the MAC register space.

SPD100

133

100 Mb/s Speed Status: This can be used to input the 100 Mb/s Speed Status

from an external phy. This is used along with the SPD1000 bit to determine

current speed status of the Phy.

SPD1000

134

1000 Mb/s Speed Status: This can be used to input the 1000 Mb/s Speed

Status from an external phy. This is used along with the SPD100 bit to

determine current speed status of the Phy.

PHYRSTN

172

Phy Reset: This pin can be used to reset an External Phy.

Serial EEPROM Interface

Symbol

Pin No(s)

Direction

Description

EESEL

EEPROM Chip Select: This signal is used to enable the external EEPROM

device.

MA4/EECLK

109

EEPROM Clock: During an EEPROM access (EESEL asserted), this pin is an

output used to drive the serial clock to an external EEPROM device.

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