DP8390D datasheet(23/56 Pages) NSC

23 / 56 page

100 Internal Registers (Continued)

103 Register Descriptions

(Continued)

TRANSMIT CONFIGURATION REGISTER (TCR)

0DH (WRITE)

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

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

543

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 D2

LB0 LB1

ENCODED LOOPBACK CONTROL

These encoded configuration bits set the type of loopback

that is to be performed Note that loopback in mode 2 sets the LPBK pin high this places the SNI

in loopback mode and that D3 of the DCR must be set to zero for loopback operation

LB1

LB0

Mode 0

Normal Operation (LPBK e 0)

Mode 1

Internal Loopback (LPBK e 0)

Mode 2

External Loopback (LPBK e 1)

Mode 3

External Loopback (LPBK e 0)

ATD

AUTO TRANSMIT DISABLE

This bit allows another station to disable the NIC’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(3an10) slot times for first three collisions

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

making a low priority mode)

reserved

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