Data Sheet

Ethernet Controller I210 — Programming Interface
454
8.12 Transmit Register Descriptions
8.12.1 Transmit Control Register - TCTL (0x0400; R/W)
Immediate
Interrupt
29 0x0 When set, packets that match this filter generate an immediate interrupt.
1588 time stamp 30 0b
When set, packets with this EType are time stamped according to the IEEE 1588
specification.
Note: The packet is time stamped only if it matches IEEE 1588 protocol
according to the definition in the TSYNCRXCTL.Type field.
Queue Enable 31 0b
When set, enables filtering of Rx packets by the EType defined in this register to
the queue indicated in this register.
Field Bit(s) Initial Value Description
Reserved 0 0b
Reserved.
Write 0b, ignore on read.
EN 1 0b
Transmit Enable.
The transmitter is enabled when this bit is set to 1b. Writing 0b to this bit stops
transmission after any in progress packets are sent. Data remains in the transmit FIFO
until the device is re-enabled. Software should combine this operation with reset if the
packets in the TX FIFO should be flushed.
Reserved 2 0b
Reserved.
Write 0b, ignore on read.
PSP 3 1b
Pad Short Packets.
0b = Do not pad.
1b = Pad.
Padding makes the packet 64 bytes long. This is not the same as the minimum
collision distance.
If padding of short packets is allowed, the total length of a packet not including FCS
should be not less than 17 bytes.
CT 11:4 0xF
Collision Threshold.
This determines the number of attempts at retransmission prior to giving up on the
packet (not including the first transmission attempt). While this can be varied, it
should be set to a value of 15 in order to comply with the IEEE specification requiring
a total of 16 attempts. The Ethernet back-off algorithm is implemented and clamps to
the maximum number of slot-times after 10 retries. This field only has meaning when
in half-duplex operation.
Note: Software can choose to abort packet transmission in less than the Ethernet
mandated 16 collisions. For this reason, hardware provides CT support.
BST 21:12 0x40
Back-Off Slot Time.
This value determines the back-off slot time value in byte time.
SWXOFF 22 0b
Software XOFF Transmission.
When set to 1b, the I210 schedules the transmission of an XOFF (PAUSE) frame using
the current value of the PAUSE timer (FCTTV.TTV). This bit self-clears upon
transmission of the XOFF frame.
Note: While 802.3x flow control is only defined during full duplex operation, the
sending of PAUSE frames via the SWXOFF bit is not gated by the duplex
settings within the I210. Software should not write a 1b to this bit while the
I210 is configured for half-duplex operation.
Field Bit(s) Initial Value Description