GD32F20x User Manual
786
SMI read operation
Applications need to operate the ENET_MAC_PHY_CTL register as follows:
1) Set the PHY device address and PHY register address and set PW to 0, so that can select
read mode.
2) Set PB bit to start reception. In the process of reception PB is always high until the receiver
is complete. Hardware will clear PB bit automatically.
The application can be aware of whether a transaction is complete or not through checking
PB bit. When PB is 1, it means the application should not change the PHY address register
contents and the PHY data register contents because of operation is running. Before writing
PB bit to 1, application must poll the PB bit until it is 0.
Note:
Because the PHY register address 16-31 register function is defined by each
manufacturer, access di
fferent PHY device’s this part should see according to the
manufacturer’s manual to adjust the parameters of applications. Details of catalog that
firmware library currently supports the PHY device can refer to firmware library related
instructions.
SMI clock selection
The SMI clock is generated by dividing application clock (AHB clock). In order to guarantee
the MDC clock frequency is no more than 2.5MHz, application should set appropriate division
factor according to the different AHB clock frequency. The following table lists the frequency
factor corresponding AHB clock selection.
Table 27-2. Clock range
AHB clock
MDC clock
Selection
35~60MHz
AHB clock/26
0x3
20~35MHz
AHB clock/16
0x2
100~120 MHz
AHB clock/62
0x1
60~100MHz
AHB clock/42
0x0
MII/RMII selection
The application can select the MII or RMII mode through the configuration bit 23 of the
AFIO_PCF0 register ENET_PHY_SEL while the Ethernet controller is under reset state or
before enabling the clocks. The MII mode is set by default.
MII: Media independent interface
The media-independent interface (MII) defines the interconnection between the MAC sub-
layer and the PHY for data transfer at 10 Mbit/s or 100 Mbit/s.
Figure 27-4. Media independent interface signals
Содержание GD32F20 Series
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