AC208-DS03-R datasheet(9/58 Pages) BOARDCOM

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Preliminary Data Sheet

AC208

07/08/02

B roa dcom

Document

AC208-DS04-405-R

Functional Description

Page 1

Sect ion 1 : F un cti o n a l Descrip t io n

FUNCTIONAL DESCRIPTION

The AC208 is an unmanaged 10/100 Mbps repeater with integrated bridge functions. The device provides eight

10/100BASE-TX twisted pair interface ports. The AC208 also includes a built-in two-segment bridge for 10/100 Mbps

connection. The AC208 provides the highest integration chip solution for dual speed hub systems. The result is ultra low

power consumption that consumes less than 1A maximum when all ports are running 100BASE-TX full-speed. The built-in

function powers down when not used (no cable detected). This reduces power consumption and improves long-term

reliability.

CLOCKS, RESET, AND POWER MANAGEMENT FUNCTIONS

The AC208 requires a single 25-MHz clock signal at the CLK input pin. An internal PLL generates all of the clock frequencies

needed by the device from the single clock input.

The AC208 can be reset in two ways:

•

During initial power on.

•

Hardware reset: A logic low signal of 10 µs pulse width applies to RST pin.

During reset, all mode pins latch in, the internal address table is initialized, and the internal state machine is reset to known

states. At the completion of the reset sequence, all ports are enabled for frame reception and transmission.

The AC208 offers the following power management:

•

Power down mode: This can be achieved by writing to register 0.11 plus port based address.

Example: Port 1 has a based address of Hex 00. During power down, the device is able to respond through the MDC/

MDIO interface.

•

Energy detect mode: The device powers down all of the unused circuitry when the cable is not installed. The Energy

Detect (ED) circuit stays on to monitor incoming signals from the media. The MDC/MDIO interface is turned on in

response to any access transaction. The transmit circuit sends out a link pulse with minimum power consumption. If a

valid signal is received from the media, the device is powered up and resumes normal transmit/receive operation.

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