UM10503
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User manual
Rev. 1.3 — 6 July 2012
755 of 1269
NXP Semiconductors
UM10503
Chapter 26: LPC43xx Ethernet
26.7.5.3.2
Receive descriptor
The structure of the received descriptor is shown in
. This can have 32 bytes of
descriptor data (8 DWORDs) when Advanced Timestamp is selected.
Remark:
The SW should set the DMA Bus Mode register[7] so that the DMA operates
with extended descriptor size. When this control bit is reset, RDES0[7] and RDES0[0] is
always cleared and the RDES4-RDES7 descriptor space are not valid.
Table 586. Transmit descriptor word 2 (TDES2)
Bit
Symbol Description
31:0
B1ADD
Buffer 1 Address Pointer
These bits indicate the physical address of Buffer 1. There is no limitation on
the buffer address alignment. See
for further detail on
buffer address alignment.
Table 587. Transmit descriptor word 3 (TDES3)
Bit
Symbol Description
31:0
B2ADD
Buffer 2 Address Pointer (Next Descriptor Address)
Indicates the physical address of Buffer 2 when a descriptor ring structure is
used. If the Second Address Chained (TDES1[24]) bit is set, this address
contains the pointer to the physical memory where the Next Descriptor is
present. The buffer address pointer must be aligned to the bus width only
when TDES1[24] is set. (LSBs are ignored internally.)
Table 588. Transmit descriptor word 6 (TDES6)
Bit
Symbol Description
31:0
TTSL
Transmit Frame Timestamp Low
This field is updated by DMA with the least significant 32 bits of the
timestamp captured for the corresponding transmit frame. This field has the
timestamp only if the Last Segment bit (LS) in the descriptor is set and
Timestamp status (TTSS) bit is set.
Table 589. Transmit descriptor word 7 (TDES7)
Bit
Symbol Description
31:0
TTSH
Transmit Frame Timestamp High
This field is updated by DMA with the most significant 32 bits of the
timestamp captured for the corresponding receive frame. This field has the
timestamp only if the Last Segment bit (LS) in the descriptor is set and
Timestamp status (TTSS) bit is set.