GD32A50x User Manual
121
state or slow down to about 20KHz.
20
PLLMEN
PLL clock monitor enable
0: Disable the PLL clock monitor
1: Enable the PLL clock monitor
PLLMEN enable the hardware detects that the PLL clock is stuck at a low/high
state.
This bit cannot be set to 1, if the PLL is disabled. It reset by hardware when entering
Deep-sleep or Standby mode or PLL unlock are detected.
19
CKMEN
HXTAL clock monitor enable
0: Disable the external 2 ~ 40 MHz crystal oscillator (HXTAL) clock monitor
1: Enable the external 2 ~ 40 MHz crystal oscillator (HXTAL) clock monitor
When the hardware detects that the HXTAL clock is stuck at a low or high state, the
internal hardware will switch the system clock to be the internal high speed IRC8M
RC clock. The way to recover the original system clock is by either an external reset,
power on reset or clearing CKMIF by software.
Note:
When the HXTAL clock monitor is enabled, the hardware will automatically
enable the IRC8M internal RC oscillator regardless of the control bit, IRC8MEN,
state.
18
HXTALBPS
External crystal oscillator (HXTAL) clock bypass mode enable
The HXTALBPS bit can be written only if the HXTALEN is 0.
0: Disable the HXTAL bypass mode
1: Enable the HXTAL bypass mode in which the HXTAL output clock is equal to
the input clock.
17
HXTALSTB
External crystal oscillator (HXTAL) clock stabilization flag
Set by hardware to indicate if the HXTAL oscillator is stable and ready for use.
0: HXTAL oscillator is not stable
1: HXTAL oscillator is stable
16
HXTALEN
External high speed oscillator enable
Set and reset by software. This bit cannot be reset if the HXTAL clock is used as
the system clock or the PLL input clock. Reset by hardware when entering Deep-
sleep or Standby mode.
0: External 2 ~ 40 MHz crystal oscillator disabled
1: External 2 ~ 40 MHz crystal oscillator enabled
15:8
IRC8MCALIB[7:0]
Internal 8M RC oscillator calibration value register
These bits are load automatically at power on.
7:3
IRC8MADJ[4:0]
Internal 8M RC oscillator clock trim adjust value
These bits are set by software. The trimming value is there bits (IRC8MADJ) added
to the IRC8MCALIB[7:0] bits. The trimming value should trim the IRC8M to 8 MHz
± 1%.