DP8390D datasheet(24/56 Pages) NSC

24 / 56 page

100 Internal Registers (Continued)

103 Register Descriptions

(Continued)

TRANSMIT STATUS REGISTER (TSR)

04H (READ)

This register records events that occur on the media during transmission of a packet It is cleared when the next transmission is

initiated by the host All bits remain low unless the event that corresponds to a particular bit occurs during transmission Each

transmission should be followed by a read of this register The contents of this register are not specified until after the first

transmission

76543210

OWC

CDH

CRS

ABT

COL

PTX

Bit

Symbol

Description

PTX

PACKET TRANSMITTED

Indicates transmission without error (No excessive

collisions or FIFO underrun) (ABT e ‘‘0’’ FU e ‘‘0’’)

reserved

COL

TRANSMIT COLLIDED

Indicates that the transmission collided at least once

with another station on the network The number of collisions is recorded in the

Number of Collisions Registers (NCR)

ABT

TRANSMIT ABORTED

Indicates the NIC aborted transmission because of

excessive collisions (Total number of transmissions including original

transmission attempt equals 16)

CRS

CARRIER SENSE LOST

This bit is set when carrier is lost during transmission

of the packet Carrier Sense is monitored from the end of PreambleSynch until

TXEN is dropped Transmission is not aborted on loss of carrier

FIFO UNDERRUN

If the NIC cannot gain access of the bus before the FIFO

empties this bit is set Transmission of the packet will be aborted

CDH

CD HEARTBEAT

Failure of the transceiver to transmit a collision signal after

transmission of a packet will set this bit The Collision Detect (CD) heartbeat

signal must commence during the first 64 ms of the Interframe Gap following a

transmission In certain collisions the CD Heartbeat bit will be set even though

the transceiver is not performing the CD heartbeat test

OWC

OUT OF WINDOW COLLISION

Indicates that a collision occurred after a slot

time (512 ms) Transmissions rescheduled as in normal collisions

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