GD32F20x User Manual
804
1. Wait the current sending frame completes and then reset the TxDMA block by clearing STE
bit in ENET_DMA_CTL register.
2. Clear the TEN and REN bit in ENET_MAC_CFG register to disable the MAC’s transmit and
receive function.
3. Check the RS bit in ENET_DMA_STAT register, waiting receive DMA read out all the
frames in the receive FIFO and then close RxDMA.
4. Configure and enable the external interrupt line 19, so that it can generate an interrupt or
event. If EXTI line 19 is configured to generate an interrupt, application still needs to modify
ENET_WKUP_IRQ interrupt handling procedures to clear the pending bit of the EXTI line 19.
5. Set the MPEN or WFEN (or both) bit in ENET_MAC_WUM register to enable Magic Packet
or Remote Wakeup frame(or both) detection.
6. Setting PWD bit in ENET_MAC_WUM register to enter power-down state.
7. Setting REN bit in ENET_MAC_CFG register to make MAC’s receive function work.
8. Make MCU enter Deep-sleep mode.
9. After received a wakeup type frame, the Ethernet module exits the power-down state.
10. Reading the ENET_MAC_WUM register to clear the power management event flags.
Enable MAC’s transmit function and enable TxDMA and RxDMA.
11. Initialize the MCU system clock: enable HXTAL and configure the RCU unit.
27.3.5.
Precision time protocol: PTP
The majority of protocols are implemented by the UDP layer application software. The PTP
module of the MAC is mainly to recording the transmitting and receiving PTP packets’
precision time and returning it to application.
Specific details about the precise time protocol (PTP) please see the document “IEEE
Standard 1588™”.
Reference clock source
System reference time in Ethernet is maintained by a 64-bit register whose high 32-bit
indicates ‘second’ time and low 32-bit indicates ‘subsecond’, this is defined in IEEE 1588
specification.
The input PTP reference clock is used to drive the system reference time (also called system
time for short) and capture timestamp value for PTP frame. The frequency of this reference
clock must be configured no less than the resolution of timestamp counter. The
synchronization accuracy between the master node and slave node is around 0.1us.
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