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Nations Technologies Inc.
Tel
：
+86-755-86309900
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Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
Bit field
Name
Description
ETH_PTPTSCTRL.TSENA is 1, transmit frame timestamp function is enabled.
0: Disable transmit frame timestamp function.
1: Enable transmit frame timestamp function.
21:11
TBS2[10:0]
Transmit buffer 2 size.
These bits give the size (in bytes) of second data buffer and are invalid if TDES1.TCH
is 1.
10:0
TBS1[10:0]
Transmit buffer 1 size.
These bits give the size (in bytes) of first data buffer, if its value is 0, DMA skips this
buffer and according to TDES1.TCH uses buffer 2 (TDES1.TCH = 0) or next
descriptor (TDES1.TCH = 1).
TDES2: Transmit descriptor word 2
Before transmit a frame, application must configure TDES2 as the address of transmit buffer 1. After data is
transmitted, DMA can use them to store the lower 32 bits of the frame's timestamp.
When the value of TDES2 represents the physical address of buffer 1, there is no restriction on the address alignment
of the cache. When the value of these bits represents the lower 32 bits of the timestamp, TDES1.TTSE and TDES1.LS
of the current descriptor must be set.
TDES3: Transmit descriptor word 3
Before transmit a frame, application must configure TDES3 as the address of transmit buffer 2, or as the address of
next descriptor (depending on whether the descriptor type is chain or ring). After data is transmitted, DMA can use
them to store the upper 32 bits of the frame's timestamp.
When the value of TDES3 represents the physical address of buffer 2 (TDES1.TCH = 0), there is no restriction on
the address alignment of the buffer. When the value of TDES3 represents next descriptor address (TDES1.TCH = 1),
these bits must be word-aligned. When the value of TDES3 represents the upper 32 bits of timestamp, TDES1.TTSE
and TDES1.LS of the current descriptor must be set.
25.4.8.3.4
Processing after sending query suspension
After the transmission is started, DMA will continuously query transmit descriptor. DMA will enter the suspended
state and suspend the transmission in the following cases. The current descriptor is fixed to the last descriptor before
suspension.
When DMA detects that TDES0.OWN is 0, that is, CPU occupies the descriptor, DMA will enter suspended
state and suspend the query. At this time, ETH_DMASTS.NIS and ETH_DMASTS.TU will be set to 1. In this
case, it is necessary to set TDES0.OWN to 1 to transfer the ownership of descriptor to DMA, and then initiate
a send query command to try to re-acquire descriptor.
In process of transmit a frame, if a data underflow error is detected, frame transmission will be suspended and
enter suspended state. TDES0.ES and TDES0.UF will be set, as will ETH_DMASTS.AIS and
ETH_DMASTS.UNF. In this case, it is still necessary to initiate a transmit query command to try to re-obtain
descriptor.
25.4.8.3.5
TxDMA operation flow
DMA operation of the sender is divided into two cases: non-OSF mode and OSF mode. By default, non-OSF mode
