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GD32F10x User Manual
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in the corresponding transmission/reception descriptor. The 64-bit timestamp information of
transmission frame is written back to the transmit descriptor and the 64-bit timestamp
information of reception frame is written back to the receive descriptor. See the detailed
description in
Transmit DMA descriptor with IEEE 1588 timestamp format
DMA descriptor with IEEE 1588 timestamp format
PTP trigger internal connection with TIMER1
MAC can provide trigger interrupt when the system time is no less than the target time. Using
an interrupt imports a known latency and an uncertainty in the command execution time. In
order to calculate the time of this known latency part, when the system time is greater than
target time, the PTP module sets an output signal. Set bit 29 of AFIO_PCF0 register to 0 can
make this signal internally connected to the ITI1 input of TIMER1. For this feature designed,
no uncertainty is introduced because the clock of the TIMER1 and PTP reference clock
(HCLK) are synchronous.
PTP pulse-per-second (PPS) output signal
Application set bit 30 of AFIO_PCF0 register to 1 to enable the PPS output function. This
function can output a signal with the pulse width of 125ms, which can be used to check the
synchronization between all nodes in the network. To test the difference between the slave
clock and the master clock, both of the slave and master can output PPS and connect them
to one oscilloscope for clock measurement.
22.3.6.
DMA controller description
Ethernet DMA controller is designed for frame transmission between FIFO and system
memory which can reduce the occupation of CPU. Communication between the CPU and the
DMA is achieved by the following two kinds of data structures:
Descriptor table (ring or chain type) and data buffer
Control and status register
Applications need to provide the memory for storage of descriptor tables and data buffers.
Descriptors that reside in the memory act as pointers to these buffers. Transmission has
transmission descriptor and reception has reception descriptor. The base address of each
table is stored in ENET_DMA_TDTADDR and ENET_DMA_RDTADDR register. Descriptors
of transmission constituted by 4 descriptor word (TDES0-TDES3). Likewise, reception
descriptors constituted by 4 descriptor word (RDES0-RDES3). Each descriptor can point to a
maximum of two buffers. The value of the buffer 2 can be programmed to the second data
address or the next descriptor address which is determined by the configured descriptor table
t
ype: Ring or Chain. Buffer space only contains frame data which are located in host’s physical
memory space. One buffer can store only one frame data but one frame data can be stored
in more than one buffer which means one buffer can only store a part of a frame. When chain
structure is set, descriptor table is an explicitly one and when ring structure is set, descriptor
Содержание GD32F10 Series
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Страница 416: ...GD32F10x User Manual 416 shadow register updates every update event ...
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Страница 518: ...GD32F10x User Manual 518 These bits are not used in SPI mode ...