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DocID022152 Rev 4 175/185
STM32F405xx, STM32F407xx Application block diagrams
Figure 92. RMII with a 25 MHz crystal and PHY with PLL
1. f
HCLK
must be greater than 25 MHz.
2. The 25 MHz (PHY_CLK) must be derived directly from the HSE oscillator, before the PLL block.
MCU
Ethernet
MAC 10/100
Ethernet
PHY 10/100
PLL
HCLK
XT1
PHY_CLK 25 MHz
RMII_RXD[1:0]
RMII_CRX_DV
RMII_REF_CLK
RMII_TX_EN
RMII_TXD[1:0]
MDIO
MDC
HCLK
(1)
STM32F
TIM2
Timestamp
comparator
Timer
input
trigger
IEEE1588 PTP
RMII
= 7 pins
RMII + MDC
= 9 pins
MS19970V1
/2 or /20
synchronous
2.5 or 25 MHz 50 MHz
XTAL
25 MHz
OSC
PLL
REF_CLK
MCO1/MCO2