VSC7440 datasheet(248/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

231

To read number of transmitted yellow frames for service counter 714:

Write 714 to STAT_VIEW in QSYS::STAT_CFG.

Read QSYS::CNT[385].

To read number of discarded green octets with QoS class 4 on port 9:

Write 9 to STAT_VIEW in QSYS::STAT_CFG.

Read QSYS::CNT[76] for the least significant bits.

Read QSYS::CNT[140] for the most significant bits.

3.24.9.5 Energy Efficient Ethernet (EEE) Control

The front ports are able to signal low power idle (LPI) towards the MACs, in case they request the PHYs

to enter low power mode. A controller in each port module assures that frames are not transmitted when

the PHYs are powered down. This controller powers the PHY down when there is nothing to transmit for

a while, and it powers up the PHY when there is either data ready for a configurable time or when the

queue system has urgent data ready requiring transmission as soon as possible.

The following table lists the registers with configuring EEE.

Example: Configure the device to power up the PHYs when 10 frames are pending.

Only ports 3 through 6 should regard their data as urgent and only for priorities 6 and 7. All other data

should get transmitted when the EEE controller in the port has seen pending data for the controller

configured time.

Write 10 to QSYS::EEE_THRES:EEE_HIGH_FRAMES.

Write 0xC0 to QSYS::EEE_CFG[3–6]::EEE_FAST_QUEUES.

3.24.9.6 Calendar Setup

There are a number of logical ports, all needing bandwidth into and out of the queue system. This is

controlled through a calendar module that grants each port access to internal busses.

The following illustration shows an overview of the internal busses. All ports are connected to a port data

bus (taxi bus) and granted access to the chip core through a mux obeying the calendar decision.

Similarly, on the path towards the transmit interface, a mux controls which port transmits the next time.

Figure 69 •

Internal Bus

Table 159 •

EEE Registers Overview

Description

Replication

QSYS::EEE_CFG

Configures the priorities per port which should bring the port

alive as fast as possible.

Per port

QSYS::EEE_THRES

Configures the amount of cells or frames pending for a priority

before the port should request immediate power up.

Per port

Front

Ports

Front

Ports

Queues

Loopback VD0/VD1

TAXI_CPU

Calendar

Algorithm

TAXI_0

...

TAXI_CPU

TAXI_0

...

VSC7440 Datasheet(PDF) 248 Page - Microsemi Corporation

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