DP83936AVF datasheet(52/104 Pages) NSC

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60 SONIC-T Registers (Continued)

647 Data Configuration Register 2

(Continued)

Bit

Description

FD FULL DUPLEX

This bit programs the SONIC-T to transmit and receive simultaneously (Full Duplex) This bit should only be set when

used in conjunction with a port that supports and is configured for Full Duplex Ethernet

0 Disable full duplex mode

1 Enable full duplex mode

PH PROGRAM HOLD

When this bit is set to ‘‘0’’ the HOLD request output is asserteddeasserted from the falling edge of bus clock If this

bit is set to ‘‘1’’ HOLD will be asserteddeasserted

clock later on the rising edge of bus clock

Must be zero

PCM PACKET COMPRESS WHEN MATCHED

When this bit is set to a ‘‘1’’ (and the PCNM bit is reset to a ‘‘0’’) the PCOMP output will be asserted if the

destination address of the packet being received matches one of the entries in the CAM (Content Addressable

Memory) This bit along with PCNM is used with the Management Bus of the DP83950 Repeater Interface

Controller (RIC) See the DP83950 datasheet for more details on the RIC Management Bus This mode is also called

the Managed Bridge Mode

Note 1

Setting PCNM and PCM to ‘‘1’’ at the same time is not allowed

Note 2

If PCNM and PCM are both ‘‘0’’ the PCOMP output will remain TRI-STATE until PCNM or PCM are changed

PCNM COMPRESS WHEN NOT MATCHED

When this bit is set to a ‘‘1’’ (and the PCM bit is set to ‘‘0’’) the PCOMP output will be asserted if the destination

address of the packet does not match one of the entries in the CAM See the PCM bit above This mode is also

called the Managed Hub Mode

Note

PCOMP will not be asserted if the destination address is a broadcast address This is true regardless of the state of the BRD bit in the

Receive Control Register

RJCM REJECT ON CAM MATCH

When this bit is set to ‘‘1’’ the SONIC-T will reject a packet on a CAM match Setting RJCM to ‘‘0’’ causes the

SONIC-T to operate normally by accepting packets on a CAM match Setting this mode is useful for a small bridge

with a limited number of nodes attached to it RJCM only affects the CAM though Setting RJCM will not invert the

function of the BRD PRO or AMC bits (to accept broadcast all physical or multicast packets respectively) in the

Receive Control Register (see Section 643) This means for example that it is not possible to set RJCM and BRD

to reject all broadcast packets If RJCM and BRD are set at the same time however all broadcast packets will be

accepted but any packets that have a destination address that matches an address in the CAM will be rejected

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DP83936AVF Datasheet(PDF) 52 Page - National Semiconductor (TI)

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