DocID025202 Rev 7
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RM0365
Reset and clock control (RCC)
154
Bits 21:18
PLLMUL:
PLL multiplication factor
These bits are written by software to define the PLL multiplication factor. These bits can be
written only when PLL is disabled.
Caution: The PLL output frequency must not exceed 72 MHz.
0000: PLL input clock x 2
0001: PLL input clock x 3
0010: PLL input clock x 4
0011: PLL input clock x 5
0100: PLL input clock x 6
0101: PLL input clock x 7
0110: PLL input clock x 8
0111: PLL input clock x 9
1000: PLL input clock x 10
1001: PLL input clock x 11
1010: PLL input clock x 12
1011: PLL input clock x 13
1100: PLL input clock x 14
1101: PLL input clock x 15
1110: PLL input clock x 16
1111: PLL input clock x 16
Bit 17
PLLXTPRE:
HSE divider for PLL input clock
This bits is set and cleared by software to select the HSE division factor for the PLL. It can be
written only when the PLL is disabled.
Note: This bit is the same as the LSB of PREDIV in
Clock configuration register 2
(for compatibility with other STM32 products)
0000: HSE input to PLL not divided
0001: HSE input to PLL divided by 2
Bits 16:15
PLLSRC
: PLL entry clock source (STM32F302xD/E only)
Set and cleared by software to select PLL clock source. These bits can be written only when
PLL is disabled.
00: HSI/2 used as PREDIV1 entry and PREDIV1 forced to div by 2.
01: HSI used as PREDIV1 entry.
10: HSE used as PREDIV1 entry.
11: Reserved.
Bit 16
PLLSRC:
PLL entry clock source
Set and cleared by software to select PLL clock source. This bit can be written only when PLL
is disabled.
0: HSI/2 selected as PLL input clock
1: HSE/PREDIV selected as PLL input clock (refer to
Section 9.4.12: Clock configuration
register 2 (RCC_CFGR2) on page 148
Bit 15 Reserved, must be kept at reset value in STM32F302xB/C and STM32F302x6/8 devices, and
used with Bit 16 in STM32F302xD/E to select the PLL clock source.
Bit14 Reserved, must be kept at reset value.