
GD32F10x User Manual
691
store the whole frame data. When the last descriptor is fetched and buffer finished reading,
the transmitting status will write back to it. The other descriptors (here means the descriptor
whose LSG bit is reset) of the current frame will not be changed by TxDMA controller except
the DAV bit will be reset to 0. After starting transfer frame data from memory to FIFO, the
transmitting has not actually start. The real start time for sending frame on interface is
depended on TxDMA mode: Cut-Through mode or Store-and-Forward mode. The former
mode starts sending when the byte number of FIFO is greater than configured threshold and
the latter mode starts sending when the whole frame data are transferred into FIFO or when
the FIFO is almost full.
Suspend during transmit polling
The DMA controller keeps querying the transmit descriptor after the transmission is started.
If either of the following conditions happens, the DMA controller will enter suspend state and
the transmit polling will stop. Though the DMA entered suspend state, the descriptor pointer
is maintained to the descriptor following of the last closed descriptor.
The DMA controller fetches a descriptor with DAV=0, then it enters suspend state and
stops polling. In this case, the NI bit and TBU bit in ENET_DMA_STAT register are set.
The MAC FIFO is empty during sending a frame on interface which means an error of
underflow occurs. In this case, the AI bit and TU bit in ENET_DMA_STAT register are
set. Also the transmit error status will write back to transmit descriptor.
Transmit DMA descriptor with IEEE 1588 timestamp format
When TTSEN bit is set, the timestamp function is enabled. The TxDMA controller writes
transmit timestamp status TTMSS and timestamp back to descriptor TDES2 and TDES3 after
the frame transmission complete.
TxDMA descriptors
The TxDMA descriptor structure consists of four 32-bit words: TDES0 ~ TDES3. The
descriptions of TDES0, TDES1, TDES2 and TDES3 are given below:
Note
: When a frame is described by more than one descriptor, only the control bits of the first
descriptor are accept by TxDMA controller (except INTC). But the status and timestamp (if
enabled) are written back to the last descriptor.
Figure 22-9. Transmit descriptor
Содержание GD32F10 Series
Страница 1: ...GigaDevice Semiconductor Inc GD32F10x Arm Cortex M3 32 bit MCU User Manual Revision 2 6 Jun 2022 ...
Страница 63: ...GD32F10x User Manual 63 programmed during the chip production ...
Страница 117: ...GD32F10x User Manual 117 010 1 0 011 0 9 ...
Страница 416: ...GD32F10x User Manual 416 shadow register updates every update event ...
Страница 427: ...GD32F10x User Manual 427 value ...
Страница 518: ...GD32F10x User Manual 518 These bits are not used in SPI mode ...