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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
895 of 1441
NXP Semiconductors
UM10503
Chapter 28: LPC43xx/LPC43Sxx Ethernet
20
TCH
Second Address Chained
When set, this bit indicates that the second address in the descriptor is the Next Descriptor address
rather than the second buffer address. When TDES0[20] is set, TBS2 (TDES1[28:16]) is a “don’t
care” value. TDES0[21] takes precedence over TDES0[20].
21
TER
Transmit End of Ring
When set, this bit indicates that the descriptor list reached its final descriptor. The DMA returns to
the base address of the list, creating a descriptor ring.
23:22
-
Reserved
24
-
Reserved
25
TTSE
Transmit Timestamp Enable
When set, this bit enables IEEE1588 hardware Time stamping for the transmit frame referenced by
the descriptor. This field is valid only when the First Segment control bit (TDES0[28]) is set.
26
DP
Disable Pad
When set, the MAC does not automatically add padding to a frame shorter than 64 bytes. When this
bit is reset, the DMA automatically adds padding and CRC to a frame shorter than 64 bytes, and the
CRC field is added despite the state of the DC (TDES0[27]) bit. This is valid only when the first
segment (TDES0[28]) is set.
27
DC
Disable CRC
When this bit is set, the MAC does not append a cyclic redundancy check (CRC) to the end of the
transmitted frame. This is valid only when the first segment (TDES0[28]) is set.
28
FS
First Segment
When set, this bit indicates that the buffer contains the first segment of a frame.
29
LS
Last Segment
When set, this bit indicates that the buffer contains the last segment of the frame. When this bit is
set, the TBS1: Transmit Buffer 1 Size or TBS2: Transmit Buffer 2 Size field in TDES1 should have a
non-zero value.
30
IC
Interrupt on Completion
When set, this bit sets the Transmit Interrupt (Register 5[0]) after the present frame has been
transmitted.
31
OWN
Own Bit
When set, this bit indicates that the descriptor is owned by the DMA. When this bit is reset, it
indicates that the descriptor is owned by the Host. The DMA clears this bit either when it completes
the frame transmission or when the buffers allocated in the descriptor are read completely. The
ownership bit of the frame’s first descriptor must be set after all subsequent descriptors belonging to
the same frame have been set. This avoids a possible race condition between fetching a descriptor
and the driver setting an ownership bit.
Table 654. Transmit descriptor word 0 (TDES0)
Bit
Symbol
Description
Table 655. Transmit descriptor word 1 (TDES1)
Bit
Symbol Description
12:0
TBS1
Transmit buffer 1 size
These bits indicate the first data buffer byte size, in bytes. If this field is 0, the
DMA ignores this buffer and uses Buffer 2 or the next descriptor, depending
on the value of TCH (TDES0[20]).
15:13
-
Reserved
28:16
TBS2
These bits indicate the second data buffer size in bytes. This field is not valid
if TDES0[20] is set. See
.
31:29
-
Reserved