MU9C8358 データシートの表示（PDF） - Music Semiconductors

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MU9C8358

Quad 10/100Mb Ethernet Filter Interface

Music Semiconductors 

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Once configured, the MU9C8358 will extract the DA from

the frames that are received through the MII ports. An

automatic address processing function is subsequently

triggered. Once the DA processing function is triggered,

the frame is monitored to detect whether it is a broadcast,

multicast, or unicast frame and the appropriate actions are

taken. DA processing consists of the following actions:

• Packets are characterized as Broadcast, Multicast, or

Unicast types.

• Unicast packets initiate a search of the CAM for

existing entries.

• If a DA match is found, the Port ID read from the

CAM is compared to the Source Port ID. If the Source

Port ID and Destination Port ID match, the frame is

rejected. If the Port IDs are different, the Tag

information is made available for MACs that support

Tag switching, through the Tag port.

• If the MU9C8358 rejects the frame, it asserts the

Reject output pin (REJ) and forces the MII RX_ER

output (FRX_ER) HIGH for the appropriate MII Port.

This causes the MAC to discard the frame.

• Once the DA processing function is complete, the

MU9C8358 stores the result. This result indicates the

characterization of the processed frame. (Broadcast,

Multicast, or Unicast) and the Source Port ID.

Additionally, if a unicast frame was processed, the

result of the search and the port ID of the DA is also

stored. Finally, the detail of whether the Destination

port and the Source port are identical is also stored.

• The result of DA processing may be read in two ways.

An interrupt may be sent to the host processor

indicating that there is a result available. The host

processor would read the result from an internal

Result Data register. Alternatively, external circuitry

can monitor the status of the Result Port Data valid

(RP_DV) output pin. This output indicates that there

is a result available at the Result port. The external

circuitry can read the data by asserting the Result Port

Select (RP_SEL) pin. Assertion of Result Port Next

(RP_NXT) clears the value and advances the next

entry if there is one available.

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Once configured, the MU9C8358 also will perform SA

processing functions after the address information has

been extracted from a received frame. The SA of each

arriving frame is stored by the MU9C8358 for further

processing, along with the ID of the port on which it

arrived, and the current time stamp. Note that at start-up,

permanent addresses and Port IDs are loaded into the

LANCAM through the CPU port; as message traffic

proceeds, new addresses are learned and added to the

LANCAM database, and aged addresses are purged. SA

processing consists of the following actions:

• The SA field is collected and temporarily stored. Note

the SA cannot be a Broadcast or Multicast address by

definition.

• When the complete packet has arrived, the CRC field

is checked and the length of the packet is checked (if

the CRC facility is enabled and the packet is

10 Base - X). Any errors result in no further SA

processing.

• If the packet did not contain any errors, the SA field is

compared with the address fields that are stored in the

LANCAM.

• If a match is found, the Port ID and time stamp for

that entry are updated. If no match is found, the SA is

added to the CAM, along with the current time stamp

and the Port ID assigned to that particular Source port.

See the PCFG registers section for more information on

the CRC check facility.

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