5220-DS02-R datasheet(28/90 Pages) BOARDCOM

28 / 90 page

BCM5220

Preliminary Data Sheet

04/20/04

Broa d c om Co rp o r a t i o n

Page 16

Energy Detection

Document

5220-DS04-405-R

INTERRUPT MODE

The BCM5220 can be programmed to provide an interrupt output. Three conditions can cause an interrupt to be generated:

changes in the duplex mode, changes in the speed of operation or changes in the link status. The interrupt feature is disabled

by default. When the interrupt capability is enabled by setting MII register 1Ah, bit 14, the XMTLED# pin becomes the INTR#

pin and the RCVLED# pin becomes an activity pin named ACTLED#. The INTR# pin is open-drain and can be wire-ORed

with INTR# pins of other chips on a board. The status of each interrupt source is reflected in register 1Ah, bits 1, 2 and 3. If

any type of interrupt occurs, the Interrupt Status bit, register 1Ah, bit 0, is set.

The Interrupt register (1Ah) also contains several bits to control different facets of the interrupt function. If the interrupt enable

bit is set to 0, no status bits are set and no interrupts are generated. If the interrupt enable bit is set to 1, the following

conditions apply:

•

If mask status bits (bits 9,10,11) are set to 0 and the interrupt mask (bit 8) is set to 0, status bits and interrupts are

available.

•

If mask status bits (bits 9,10,11) are set to 0 and the interrupt mask (bit 8) is set to 1, status bits are set but no interrupts

generated.

•

If any mask status bit is set to 1 and the interrupt mask is set to 0, that status bit is not set and no interrupt of that type

is generated.

•

If any mask status bit is set to 1 and the interrupt mask is set to 1, that status bit is not set and no interrupt of any kind is

generated.

ENERGY DETECTION

An on-chip energy detection circuit can determine when a link partner is connected to the end of the transmission media.

The circuit monitors the receive inputs for any type of energy, including 10BASE-T, 100BASE-TX or 100BASE-FX packets,

and 10BASE-T or auto-negotiation link pulses. When energy is detected on the receive inputs for longer than 1.3 ms, the

ENERGYDET output is asserted. If all traces of energy disappear for longer then 1.3s, it is assumed that the link partner has

disconnected, and the ENERGYDET output is deasserted. The energy detection circuit is operational in both full power and

some of the low power modes.

5220-DS02-R Datasheet(PDF) 28 Page - Broadcom Corporation.