FW322 View Datasheet(PDF) - Agere -> LSI Corporation

Part Name

Description

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FW322

1394A PCI PHY/Link Open Host Controller Interface

Agere -> LSI Corporation 

FW322

1394A PCI PHY/Link Open Host Controller Interface

Data Sheet, Rev. 1

February 2001

FW322 Functional Description (continued)

PMEs provide a hardware mechanism for requesting a

software wake-up. Together, the power management

register interface and PME support within the FW322

combine to form an efficient means for implementing

power management.

Isochronous Data Transfer

The isochronous data transfer logic handles the transfer

of isochronous data between the link core and the PCI

interface module. It consists of the isochronous register

module, the isochronous transmit DMA module, the

isochronous receive DMA module, the isochronous

transmit FIFO, and the isochronous receive FIFO.

Isochronous Register

The isochronous register module operates on PCI slave

accesses to OHCI registers within the isochronous

block. The module also maintains the status of inter-

rupts generated within the isochronous block and sends

the isochronous interrupt status to the OHCI interrupt

handler block.

Isochronous Transmit DMA (ITDMA)

The isochronous transmit DMA module moves data

from host memory to the link core, which will then send

the data to the 1394 bus. It consists of isochronous

contexts, each of which is independently controlled by

software, and can send data on a 1394 isochronous

channel.

During each 1394 isochronous cycle, the ITDMA

module will service each of the contexts and attempt to

process one 1394 packet for each context. If a context is

active, ITDMA will request access to the PCI bus. When

granted PCI access, a descriptor block is fetched from

host memory. This data is decoded by ITDMA to deter-

mine how much data is required and where in host

memory the data resides. ITDMA initiates another PCI

access to fetch this data, which is placed into the

transmit FIFO for processing by the link core. If the

context is not active, it is skipped by ITDMA for the

current cycle.

After processing each context, ITDMA writes a cycle

marker word in the transmit FIFO to indicate to the link

core that there is no more data for this isochronous

cycle.

As a summary, the major steps for the FW322 ITDMA to

transmit a packet are the following:

1. Fetch a descriptor block from host memory.

2. Fetch data specified by the descriptor block from

host memory, and place it into the isochronous

transmit FIFO.

3. Data in FIFO is read by the link and sent to the PHY

core device interface.

Isochronous Receive DMA (IRDMA)

The isochronous receive DMA module moves data from

the receive FIFO to host memory. It consists of isochro-

nous contexts, each of which is independently

controlled by software. Normally, each context can

process data on a single 1394 isochronous channel.

However, software can select one context to receive

data on multiple channels.

When IRDMA detects that the link core has placed data

into the receive FIFO, it immediately reads out the first

word in the FIFO, which makes up the header of the

isochronous packet. IRDMA extracts the channel

number for the packet and packet filtering controls from

the header. This information is compared with the

control registers for each context to determine if any

context is to process this packet.

If a match is found, IRDMA will request access to the

PCI bus. When granted PCI access, a descriptor block

is fetched from host memory. The descriptor provides

information about the host memory block allocated for

the incoming packet. IRDMA then reads the packet from

the receive FIFO and writes the data to host memory via

the PCI bus.

If no match is found, IRDMA will read the remainder of

the packet from the receive FIFO, but not process the

data in any way.

Asynchronous Data Transfer

The ASYNC block is functionally partitioned into two

independent logic blocks for transmitting and receiving

1394 packets. The ASYNC_TX unit is responsible for

packet transmission while the ASYNC_RX unit pro-

cesses received data.

Asynchronous Register

The asynchronous register module operates on PCI

slave accesses to OHCI registers within the asynchro-

nous block. The module also maintains the status ofin-

terrupts generated within the asynchronous block and

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Lucent Technologies Inc.

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