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318 Software Developer’s Manual
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.
13.4.45 TCP 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
Value
Description
TSMT 15:0 0400h TCP Segmentation Minimum Transfer
TSPBP 31:16 0100h TCP Segmentation Packet Buffer Padding