DP83821 datasheet(17/86 Pages) NSC

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3.0 Functional Description (Continued)

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3.9 EEPROM Interface

The DP83821 supports the attachment of an external

EEPROM. The EEPROM interface provides the ability for

the DP83821 to read from and write data to an external

serial EEPROM device. Values in the external EEPROM

allow default fields in PCI configuration space and I/O

space to be overridden following a hardware reset. The

DP83821 will "autoload" values from the EEPROM to these

fields in configuration space and I/O space and perform a

checksum to verify that the data is valid. If the EEPROM is

not present, the DP83821 initialization uses default values

for

the

appropriate

Configuration

and

Operational

Registers. Software can read and write to the EEPROM

using “bit-bang” accesses via the MII/EEPROM Access

3.10 Boot ROM Interface

The BIOS ROM interface allows the DP83821 to read from

and write data to an external PROM/Flash device.

3.11 Power Management and Wake Functions

The

DP83821

compliant

with

the

PCI

Power

Management Specification v1.1. The device can be

programmed to any of the powered states (D0, D1, D2,

D3hot) and enabled to assert its PMEN pin through the

Configuration Register PMCSR. In addition, the device will

enter the D3cold state when PCI power is dropped,

regardless of the programmed power state. In either D3hot

or D3cold, if PMEN assertion is enabled, the device will

keep the receiver alive so that it may recognize wake

packets and signal the system to wake up; if PMEN

assertion is not enabled, the device will go to sleep and be

unable to receive packets.

The DP83821 supports several types of wake events that

will signal the power management logic to assert PMEN.

These are detailed in the Wake On LAN section (4.2.18.1).

In order for the device to request a system wake, at least

one wake event must be configured in the Wake Command

and Status Register (WCSR). If PMEN assertion is enabled

and the device enters the D3cold state with no wake

events enabled, the device will go to sleep.

When the device is in a power management state other

than D0 (the fully alive state), the only PCI bus activity it

may initiate is the assertion of PMEN. This means any

packets received will remain in the receive FIFO until the

device is returned to the fully alive state. Upon waking up,

the wake packet is available in the receive FIFO.

In any power state, enabling PMEN assertion adds

additional packet filtering: only those packet types that are

configured as wake packets in WCSR will be accepted.

This prevents non-wake packets from filling the receive

FIFO while the device is in a low power state and

preventing a wake packet from being accepted. It is

expected that while in the fully alive state, PMEN assertion

will be disabled to eliminate the extra level of filtering.

3.12 Network Management Functions

The DP83821 allows compliance with several layer

management standards to allow a node to monitor overall

network performance. These standards are:

— RFC 1213 (MIB II),

— RFC 1643 (Ether-like MIB), and

— IEEE 802.2 Layer Management.

Many of the counters required by these standards are

easily maintained in software during normal per-packet

processing. Those counters that would either be difficult or

impossible for software to maintain are provided for in

hardware (See Section 4.2.27). The table below outlines

each required counter, the relevant standard, and how the

counter should be maintained.

Table 3-1 MIB Compliance

Counter Name

Reference

Maintained by

Derivation

RXOctetsOK

RFC 1213,

802.3 LM

software, add cmdsts.SIZE

on receive packets with

cmdsts.OK bit set.

The byte count of each successfully

received packet is added to this counter.

The packet byte count includes the

address, type, data, and FCS fields.

RXFramesOK

802.3 LM

software, increment on

receive packets with

cmdsts.OK bit set.

This counter is incremented for each packet

successfully received (this includes

broadcast, multicast, and physical address

packets).

RXBroadcastPkts

RFC 1213,

802.3 LM

software, increment on

receive packets with

cmdsts.OK set and

cmdsts.DEST set to 11.

This counter is incremented for each

broadcast packet successfully received.

RXMulticastPkts

RFC 1213,

802.3 LM

software, increment on

receive packets with

cmdsts.OK set and

cmdsts.DEST set to 10.

This counter is incremented for each

multicast packet successfully received.

RXErroredPkts

RFC 1213

hardware, see

MIB:RxErroredPkts.

This counter is incremented for each packet

received with errors. This count includes

packets which are automatically rejected

from the FIFO due to both wire errors and

FIFO overruns.

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