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GD32F20x User Manual
800
RxFIFO will discard the whole frame data and return an overflow status. Also the counter
of counting the overflow condition times will plus 1.
If the RxFIFO is configured in Store-and-Forward mode, the MAC can filter and discard
all error frames. But according to the configuration of FERF and FUF bit in
ENET_DMA_CTL register, RxFIFO can also receive and forward such error frame and
the frame that length is less than the minimum length.
If the RxFIFO is configured in Cut-Through mode, not all the error frames can be dropped.
Only when the start of frame (SOF) has not been read from RxFIFO and the receive
frame has been detected error status, the RxFIFO will discard the whole error frame.
Receive status word
After receiving a complete frame, the MAC will analysis and record some state information
about the frame and receiving process. These detail status information will write back to the
receive descriptor and DMA status flag. Application can check these flags for upper protocol
implementation.
Note:
The value of frame length is 0 means that for some reason (such as FIFO overflow or
dynamically modify the filter value in the receiving process, resulting did not pass the filter,
etc), frame data is not written to FIFO completely.
MAC loopback mode
Often, loopback mode is used for testing and debugging hardware and software system for
application. The MAC loopback mode is enabled by setting the LBM bit in ENET_MAC_CFG
register. In this mode, the MAC transmitter sends the Ethernet frame to its own receiver. This
mode is disabled by default.
27.3.3.
MAC statistics counters: MSC
For knowing the statistics situation of transmitting and receiving frames, there is a group of
counters designed for gathering statistics data. These MAC counters are called statistics
count
ers (MSC).In Section ‘Register Description’, there is a detailed description of the function
of these registers.
When the transmit frame does not appear the following situation, it can be called ‘fine frame’
and MSC transmit counters will automatically update:
Frame underflow
No carrier
Lose of carrier
Excessive deferral
Late collision
Excessive collision
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...