DP83907 datasheet(34/70 Pages) NSC

34 / 70 page

50 Register Descriptions (Continued)

TRANSMIT CONFIGURATION REGISTER (TCR)

ODH (WRITE)

The transmit configuration establishes the actions of the transmitter section of the DP83907 during transmission of a packet on

the network LB1 and LB0 which select loopback mode power up as 0

765

OFST

ATD

LB1

LB0

CRC

Bit

Symbol

Description

CRC

INHIBIT CRC

0 CRC appended by transmitter

1 CRC inhibited by transmitter

In loopback mode CRC can be enabled or disabled to test the CRC logic

D1 and

LB0 and

ENCODED LOOPBACK CONTROL

These encoded configuration bits set the type of loopback that is to be

performed Note that loopback in mode 2 places the ENDEC Module in loopback mode and that D3 of the

LB1

DCR must be set to zero for loopback operation

LB1

LB0

Mode 0

Normal Operation (LPBK e 0)

Mode 1

Internal NIC Module Loopback (LPBK e 0)

Mode 2

Internal ENDEC Module Loopback (LPBK e 1)

Mode 3

External Loopback (LPBK e 0)

ATD

AUTO TRANSMIT DISABLE

This bit allows another station to disable the DP83907’S transmitter by

transmission of a particular multicast packet The transmitter can be re-enabled by resetting this bit or by

reception of a second particular multicast packet

0 Normal Operation

1 Reception of multicast address hashing to bit 62 disables transmitter reception of multicast address

hashing to bit 63 enables transmitter

OFST

COLLISION OFFSET ENABLE

This bit modifies the backoff algorithm to allow prioritization of nodes

0 Backoff Logic implements normal algorithm

1 Forces Backoff algorithm modification to 0 to 2min(3 an 10) slot times for first three collisions then

follows standard backoff (For the first three collisions the station has higher average backoff delay

making a low priority mode)

Reserved

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