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AT32F435/437
Series Reference Manual
2022.11.11
Page 578
Rev 2.03
Figure 26-2 SMI interface signals
EMAC SMI
MDC
MDIO
PHY
Before write operation, PHY address, MII register and EMAC_MACMIIDT register must be configured
first, followed by the MII MW and MB bits, and then the SMI interface will transfer the PHY address,
PHY register address and data to the PHY. During the transaction, the contents of the
EMAC_MACMIIADDR and the EMAC_MACMIIDT registers are not allowed to change.
Before read operation, the PHY address and MII register must be configured first, and then the MB bit
is set and MW bit is set to 0 in the EMAC_MACMIIADDR register.
The SMI interface sends the PHY address and PHY register address, and then starts reading the PHY
register contents. During the transaction, the MB bit is always set. It is cleared by the SMI interface at
the end of read operation. Attention should be paid to the fact that the contents of the
EMAC_MACMIIADDR and EMAC_MACMIIDT registers are not allowed to change (The application
should not change these register contents. After the transaction, the EMAC_MACMIIDT register is
automatically updated with the data read from the SMI)
The SMI clock source is a divided AHB clock. The divide factor depends on the ABH clock frequency.
Note that the divide factor must be configured correctly since the MDC frequency must not be greater
than 2.5MHz.
Table 26-1 shows the clock range.
Selection bit
AHB clock
MDC clock
0000
60~100MHz
AHB clock/42
0001
100~150MHz
AHB clock/62
0010
20~35MHz
AHB clock/16
0011
35~60MHz
AHB clock/26
0100
150~250MHz
AHB clock/102
0101
250~288MHz
AHB clock/124
0110,0111
Reserved
--
Media-independent interface: MII
The media-independent interface (MII) acts an interconnection between the MAC sublayer and the PHY
for data transfer at 10Mbit/s and 100Mbit/s.