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GD32F20x User Manual
788
MAC detected an error in the receiving process. The specific error reason needs to cooperate
with the state of the MII_RX_DV and the MII_RXD[3:0] data value (see Table 27-3).
Table 27-3. Rx interface signal encoding
MII_RX_ER
MII_RX_DV
MII_RXD[3:0]
Description
0
0
0000 to 1111
Normal inter-frame
0
1
0000 to 1111
Normal reception frame data
1
0
0000
Normal inter-frame
1
0
0001 to 1101
Reserved
1
0
1110
False carrier indication
1
0
1111
Reserved
1
1
0000 to 1111
Data reception with errors
MII clock sources
To generate both TX_CLK and RX_CLK clock signals, the external PHY needs an external
25MHz clock. This 25MHz clock does not require the same one with MAC clock. It can use
the external 25MHz crystal or the output clock of microcontroller’s CK_OUT0 pin. If the clock
source is selected from CK_OUT0 pin, the MCU needs to configure the appropriate PLL to
ensure the output frequency of CK_OUT0 pin is 25MHz.
RMII: Reduced media independent interface
The reduced media-independent interface (RMII) specification reduces the pin count during
Ethernet communication. According to the IEEE 802.3 standard, an MII contains 16 pins for
data and control. The RMII specification is dedicated to reduce the pin count to 7.
The RMII block has the following characteristics:
- The clock signal needs to be increased to 50MHz and only one clock signal.
- MAC and external PHY use the same clock source
- Using the 2-bit wide data transceiver
Figure 27-5. Reduced media-independent interface signals
PHY
MAC Controller
TX_EN
TXD[1:0]
CRS_DV
RXD[1:0]
REF_CLK
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 ...