DP83902AVF datasheet(31/70 Pages) NSC

31 / 70 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 ST-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

Transmission is not aborted on loss of carrier

FIFO Underrun

If the ST-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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