GD32F403xx User Manual
86
1001: CK_PLL2 clock divided by 2 selected
1010: EXT1
selected
1011: CK_PLL2 clock selected
23:22
USBFSPSC[1:0]
USBFS clock prescaler selection
Set and reset by software to control the USBFS clock prescaler value. The USBFS
clock must be 48MHz. These bits can’t be reset if the USBFS clock is enabled.
000: CK_USBFS = CK_PLL / 1.5
001: CK_USBFS = CK_PLL
010: CK_USBFS = CK_PLL / 2.5
011: CK_USBFS = CK_PLL / 2
100: CK_USBFS = CK_PLL / 3
101: CK_USBFS = CK_PLL / 3.5
11x :CK_USBFS = CK_PLL / 4
21:18
PLLMF[3:0]
The PLL clock multiplication factor
Bit 29, bit 30 of RCU_CFG0 and these bits are written by software to define the
PLL multiplication factor
Caution: The PLL output frequency must not exceed 168 MHz
000000: (PLL source clock x 2)
000001: (PLL source clock x 3)
000010: (PLL source clock x 4)
000011: (PLL source clock x 5)
000100: (PLL source clock x 6)
000101: (PLL source clock x 7)
000110: (PLL source clock x 8)
000111: (PLL source clock x 9)
001000: (PLL source clock x 10)
001001: (PLL source clock x 11)
001010: (PLL source clock x 12)
001011: (PLL source clock x 13)
001100: (PLL source clock x 14)
001101: (PLL source clock x 6.5)
001110: (PLL source clock x 16)
001111: (PLL source clock x 16)
010000: (PLL source clock x 17)
010001: (PLL source clock x 18)
010010: (PLL source clock x 19)
010011: (PLL source clock x 20)
010100: (PLL source clock x 21)
010101: (PLL source clock x 22)
010110: (PLL source clock x 23)
010111: (PLL source clock x 24)
011000: (PLL source clock x 25)
011001: (PLL source clock x 26)