dp83901a National Semiconductor Corporation, dp83901a Datasheet - Page 27

• Manufacturer Part Number: dp83901a
• Description: Serial Network Interface Controller
• Manufacturer: National Semiconductor Corporation

10 0 Internal Registers
10 3 REGISTER DESCRIPTIONS (Continued)
TRANSMIT STATUS REGISTER (TSR)
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
Bit
D0
D1
D2
D3
D4
D5
D6
D7
PTX
Reserved
COL
ABT
CRS
FU
CDH
OWC
Symbol
Packet Transmitted Indicates transmission without error (No excessive collisions or FIFO
underrun) (ABT
Reserved
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)
Transmit Aborted Indicates the SNIC aborted transmission because of excessive collisions
(Total number of transmissions including original transmission attempt equals 16 )
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 SNIC cannot gain access of the bus before the FIFO empties this bit is
set Transmission of the packet will be aborted
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
6 4 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
Out of Window Collision Indicates that a collision occurred after a slot time (51 2 ms)
Transmissions rescheduled as in normal collisions
OWC
7
(Continued)
CDH
04H (READ)
6
e
‘‘0’’ FU
FU
5
e
CRS
4
‘‘0’’)
27
ABT
3
Description
COL
2
1
PTX
0