Intel Intel Gigabit Ethernet Controllers, PCI-X manual Tspbp Tsmt

Register Descriptions

The transmit interrupt delay timer (TIDV) can be used to coalesce transmit interrupts. However, it might be necessary to ensure that no completed transmit remains unnoticed for too long an interval in order ensure timely release of transmit buffers. This register can be used to ENSURE that a transmit interrupt occurs at some predefined interval after a transmit is completed. Like the delayed-transmit timer, the absolute transmit timer ONLY applies to transmit descriptor operations where (a) interrupt-based reporting is requested (RS set) and (b) the use of the timer function is requested (IDE is set).

This feature operates by initiating a countdown timer upon successfully transmitting the buffer. When the timer expires, a transmit-complete interrupt (ICR.TXDW) is generated. The occurrence of either an immediate (non-scheduled) or delayed transmit timer (TIDV) expiration interrupt halts the TADV timer and eliminates any spurious second interrupts.

Setting the value to 0b disables the transmit absolute delay function. If an immediate (non- scheduled) interrupt is desired for any transmit descriptor, the descriptor IDE should be set to 0b.

13.4.45TCP Segmentation Pad And Minimum Threshold

TSPMT (03830h; RW)

This register specifies fields affecting the Ethernet controller behavior during TCP Segmentation operations. Values are specified in bytes. For normal (non TCP Segmentation) operations, the Ethernet controller’s transmit DMA never begins servicing an individual data descriptor unless the transmit Packet Buffer has sufficient room to accept all of the data associated with the descriptor. However, for TCP Segmentation operations, it might be desirable to use a data descriptor that refers to a larger contiguous buffer in host memory than is actually allocated for the transmit Packet Buffer. For TCP segmentation, then, the transmit DMA is able to initiate smaller transfers than the entire descriptor’s data length field.

31 16 15 0

TSPBP

TSMT

Field	Bit(s)	Initial	Description
		Value
TSMT	15:0	0400h	TCP Segmentation Minimum Transfer
TSPBP	31:16	0100h	TCP Segmentation Packet Buffer Padding

318 Software Developer’s Manual