AM79C989JC datasheet(12/37 Pages) AMD

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Am79C989

PRELIMINARY

Management Interface

MDC

Management Data Clock

Input

MDC provides the timing reference for data on the

MDIO pin. The Management Interface provides read

and write access to QuEST registers, similar to the MII

management interface of the IEEE 802.3u standard.

MDIO

Management Data I/O

Input/Output

MDIO is a bidirectional data signal between QuEST

and a management entity. MDIO timing is referenced to

MDC. The Management Interface provides read and

write access to QuEST registers, similar to the MII

management interface of the IEEE 802.3u standard.

Miscellaneous Pins

SCLK

System Clock

Input

SLCK is a 40-MHz (100 ppm) clock used for timing the

10BASE-T ports, the (optional) AUI port, the QuASI in-

terface and core logic.

REXT

External Resistor

Input

REXT should be pulled to analog VDD via a 13 K

Ω (1%

tolerance) external resistor. This signal is used to deter-

mine the 10BASE-T transmit current reference.

QRST/STRB

QuEST Reset and Channel 0 Strobe

Input

QRST/STRB is an active-low signal that will reset

QuEST if asserted for at least 1

µs. QRST/STRB also

forces the channel slots of the QuASI interface to be

continuous aligned if strobed for a single clock period.

Power Pins

VDD

Digital Power

Power

There is a single power supply pin that is used for inter-

nal digital circuitry. The VDD pin must be connected to

a +5 V supply.

VSS

Digital Ground

Power

There is a single ground pin that is used for internal dig-

ital circuitry. The VSS pin must be connected to ground.

VDDIO

Digital I/O Power

Power

There is a single power supply pin that is used for digi-

tal I/O pins. The VDDIO pin can be connected to either

a +5 V or a +3.3 V supply.

VSSIO

Digital I/O Ground

Power

There is a single ground pin that is used for digital I/O

pins. The VSSIO pin must be connected to ground.

VDDTX

Analog 10BASE-T Power

Power

There are three power supply pins that are used for an-

alog 10BASE-T transmit pins. The VDDTX pins must

be connected to a +5 V supply.

VSSTX

Analog 10BASE-T Ground

Power

There are two ground pins that are used for analog

10BASE-T transmit pins. The VSSTX pins must be

connected to ground.

VSSRX

Analog 10BASE-T Ground

Power

There is a single ground pin that is used for analog

10BASE-T receive pins. The VSSRX pin must be con-

nected to ground.

VSSAUI

Analog I/O Ground

Power

There is a single ground pin that is used for analog AUI

circuitry. The VSSAUI pin must be connected to

ground.

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