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DM9008

ISA/Plug & Play Super Ethernet Contoller

Davicom Semiconductor, Inc. 

Transmit Configuration Register (TCR)

DM9008

ISA/Plug & Play Super Ethernet Contoller

The transmit configuration register determines the actions of the transmitter section of the DM9008 during transmission of a packet on

the network. LB1 and LB0 power up as 0.

7

6

5

4

3

2

1

0

--

--

--

OFST

ATD

LB1

LB0

CRC

Bit

Symbol

Description

D0

CRC

Inhibit CRC

0: CRC appended by transmitter

1: CRC inhibited by transmitter

D1

LB0

Encoded Loopback Control: These encoded configuration bits set the type of loopback that

D2

LB1

is to be performed. Note that loopback in mode 2 sets the ENA in loopback mode and

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

LB1

Mode 0 0

Mode 1 0

Mode 2 1

Mode 3 1

LB0

0

Normal Operation

1

ENC module Loopback

0

ENA module Loopback

1

Loopback to Coax

D3

ATD

Auto Transmit Disable: This bit allows another station to disable the DM9008 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

D4

OFST

Collision Offset Enable: This bit modifies the backoff algorithm to allow propitiation of

nodes

0: Backoff Logic implements normal algorithm

1: Forces Backoff algorithm modification to 0 to 2 min(3+n,10) slot times for first

three collisions, then follows standard backoff. (For first three collisions, station has

higher average backoff delay, resulting in a low priority mode.)

D5

--

Reserve must be set to zero

D6

--

Reserved

D7

--

Reserved

Final

17

Version: DM9008-DS-F02

November 30, 2000

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