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GD32F10x User Manual
669
of time. If the application sets transmit flow control bit TFCEN in ENET_MAC_FCTL register,
MAC will generate and transmit a pause frame when either of two conditions is satisfied in
Full-duplex mode. There are two conditions to start transmit pause frames:
1)
Application sets FLCB/BKPA bit in ENET_MAC_FCTL register to immediately send a
pause frame. When doing this, MAC sends a pause frame right now with the pause time
value PTM configured in ENET_MAC_FCTL register. If application considers the pause
time is no need any more because the transmit frame can be transmitted without pause
time, it can end the pause time by setting the pause time value PTM bits in
ENET_MAC_FCTL register to 0 and set FLCB/BKPA bit to send this zero pause time
frame.
2)
MAC automatically sends pause time when the RxFIFO is in some condition. When MAC
is receiving frame, RxFIFO will be fill in many receive data. At same time RxFIFO pops
out data to RxDMA for forwarding to memory. If the popping frequency is lower than MAC
pushing frequency, the number of bytes in RxFIFO is getting great. Once the data
amount in RxFIFO is greater than the active threshold value (RFA bits in
ENET_MAC_FCTH) of flow control, MAC will send a pause frame with PTM value in it.
After sending pause frame, MAC will start a counter with configured reload value PLTS
in ENET_MAC_FCTL register, when configured PLTS time has spent, the MAC will
check RxFIFO again. If the byte number in RxFIFO is also greater than active threshold
value, the MAC sends a pause time again. When the byte number of RxFIFO is lower
than the de-active threshold value, MAC maybe send a pause frame with zero time value
in frame’s pause time field if DZQP bit in ENET_MAC_FCTL register is reset. This zero-
pause time frame can inform send station that RxFIFO is almost empty and can receive
new data again.
Transmit inter-frame gap management
MAC can manage the interval time between two frames. This interval time is called frame gap
time. For Full-duplex mode, after complete sending a frame or MAC entered idle state, the
gap time counter starts counting. If another transmit frame presents before this counter has
not reach the configured IGBS bit time in ENET_MAC_CFG register, this transmit frame will
be pended unless the counter reach the gap time. But if the second transmit frame presents
after the gap time counter has reached the configured gap time, this frame will send
immediately. For Half-duplex mode, the gap time counter follows the Truncated Binary
Exponential Backoff algorithm. Briefly speaking, the gap time counter starts after the previous
frame has completed transmitting on interface or the MAC entered idle state, and there are
three conditions may occur during the gap time:
1) The carrier sense signal active in the first 2/3 gap period. In this case, the counter will
reload and restart.
2) The carrier sense signal active in the last 1/3 gap period. In this case, the counter will
not reload but continue counting, and when reaches gap time, the MAC sends the
second frame.
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 ...