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AT32F435/437
Series Reference Manual
2022.11.11
Page 74
Rev 2.03
Bit 0
HICKEN
0x1
rw
High speed internal clock enable
This bit is set and cleared by software. It can also be set by
hardware when exiting Standby or Deepsleep mode. When
a HEXT clock failure occurs. This bit can also be set. When
the HICK is used as the system clock, this bit cannot be
cleared.
0: Disabled
1: Enabled
4.3.2
PLL clock configuration register (CRM_PLLCFG)
Access: 0 wait state, accessible by words, half-words and bytes.
Bit
Name
Reset value
Type
Description
Bit 31: 23 Reserved
0x000
resd
Kept at its default value.
Bit 22
PLLRCS
0x0
rw
PLL reference clock select
The PLL reference clock source is selected by setting or
resetting this bit. This bit can be written only when the PLL
is disabled.
0: HICK is used as PLL reference clock
1: HEXT is used as PLL reference clock
Bit 21: 19 Reserved
0x0
resd
Kept at its default value.
Bit 18: 16 PLL_FR
0x3
rw
PLL post-division
PLL_FR range (2~5)
000: Reserved. Do not use.
001: Reserved. Do not use.
010: PLL post-division=4
011: PLL post-division=8
100: PLL post-division=16
101: PLL post-division=32
Others: Reserved. Do not use.
Attention should be paid to the correlation between the
PLL_FR value and post-division factor.
Bit 15
Reserved
0x0
resd
Kept at its default value.
Bit 14: 6 PLL_NS
0x0C0
rw
PLL multiplication factor
PLL_NS range (31~500)
000000000 ~ 000011110: Forbidden
000011111: 31
000100000: 32
000100001: 33
……
111110011: 499
111110100: 500
111110101~111111111: Forbidden
Bit 5: 4
Reserved
0x0
resd
Kept at its default value.
Bit 3: 0
PLL_MS
0x2
rw
PLL pre-division
PLL_MS range (1~15)
0000: Forbidden
0001: 1
0010: 2
0011: 3
……
1110: 14
1111: 15
Note: PLL clock formulas:
PLL output clock = PLL input clock x PLL frequency multiplication factor / (PLL pre-divider factor x PLL
post-divider factor)
500MHz <= PLL input clock x PLL frequency multiplication factor / PLL pre-divider factor <= 1200MHz
2MHz <= PLL input clock / PLL pre-divider factor <= 16MHz