AT32F425
Series Reference Manual
2022.03.30
Page 422
Ver 2.01
Bit 7: 6
Reserved
0x0
rw
Forced by hardware to 0
Bit 5
CALRDYIEN
0x0
rw
CALRDY interrupt enable
This bit is set or cleared by software.
0: Interrupt generation disabled
1: ACC interrupt is generated when CALRDY=1 in the
ACC_STS register
Bit 4
EIEN
0x0
rw
RSLOST error interrupt enable
This bit is set or cleared by software.
0: Interrupt generation disabled
1: ACC interrupt is generated when RSLOST=1 in the
ACC_STS register
Bit 3: 2
Reserved
0x0
rw
Forced by hardware to 0
Bit 1
ENTRIM
0x0
rw
Enable trim
This bit is set or cleared by software.
0: HICKCAL is calibrated.
1: HICKTRIM is calibrated.
Note: It is recommended to set ENTRIM=1 in order to get
higher calibration accuracy.
Bit 0
CALON
0x0
rw
Calibration on
This bit is set or cleared by software.
0: Calibration disabled
1: Calibration enabled, and starts searching for a pulse on
the USB_SOF.
Note: This module cannot be used without the USB_SOF
reference signal. If there are no requirements on the
accuracy of the HICK clock, it is unnecessary to enable
this module.
21.6.4 Control register 2 (ACC_CTRL2)
Bit
Register
Reset value
Type
Description
Bit 31: 14 Reserved
0x00000
resd
Forced to 0 by hardware
Bit 13: 8
HICKTRIM
0x00
ro
Internal high-speed auto clock trimming
This field is read only, but not written.
Internal high-speed clock is adjusted by ACC module,
which is added to the ACC_HICKCAL[7: 0] bit. These bits
allow the users to input a trimming value to adjust the
frequency of the HICKRC oscillator according to the
variations in voltage and temperature.
The default value is 32, which can trim the HICK to
8MHz±0.25. The trimming value is 20kHz (design value)
between two consecutive ACC_HICKTRIM steps.
Bit 7: 0
HICKCAL
0x00
ro
Internal high-speed auto clock calibration
This field is read only, but not written.
Internal high-speed clock is adjusted by ACC module.
These bits allow the users to input a trimming value to
adjust the frequency of the HICKPC oscillator according to
the variations in voltage and temperature.
The default value is 128, which can trim the HICK to
8MHz±0.25. The trimming value is 40kHz (design value)
between two consecutive ACC_HICKCAL steps.
21.6.5 Compare value 1 (ACC_C1)
Bit
Register
Reset value
Type
Description
Bit 31: 16 Reserved
0x0000
resd
Forced to 0 by hardware
Bit 15: 0
C1
0x1F2C
rw
Compare 1
This value is the lower boundary for triggering calibration,
and its default value is 7980. When the number of clocks
sampled by ACC in 1ms period is less than or equal to C1,
auto calibration is triggered automatically.
When the actual sampling value (number of clocks in 1ms)
is greater than C1 but less than C3, auto calibration is not
enabled.