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Software Developer’s Manual 315
Register Descriptions
Table 13-84. TIDV Register Bit Description
13.4.42 TX DMA Control (82544GC/EI only)
TXDMAC (03000h; R/W)
This register controls the transmit DMA pre-fetching and preemption abilities.
Table 11-85. TXDMAC Register Bit Description
13.4.43 Transmit Descriptor Control
TXDCTL (03828h; R/W)
This register controls the fetching and write back of transmit descriptors. The three threshold
values provided are used to determine when descriptors are read from and written to host memory.
The values can be in units of cache lines or descriptors (each descriptor is 16 bytes).
31 16 15 0
Reserved IDV
Field Bit(s)
Initial
Value
Description
IDV 15:0 X
Interrupt Delay Value
Counts in units of 1.024 µs. A value of 0bis not allowed.
Reserved 31:16 0b
Reserved
Reads as 0b. Should be written to 0b for future compatibility.
31 10
Reserved DPP
Field Bit(s)
Initial
Value
Description
DPP 0 1
Disable packet prefetching
When set, prevents the Ethernet controller from starting a
transmit descriptor data fetch before it has finished processing
the previous descriptor. In general, performance increases
when this bit is set to 0b.
Reserved 31:1 0
Reserved
Reads as 0b. Should be written to 0b for future compatibility.