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GD32F403xx User Manual
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source (external or internal reset).
Figure 5-1. The system reset circuit
Fi lter
WWDGT_RSTn
FWDGT_RSTn
SW_RSTn
OB_STDBY_RSTn
OB_DPSLP_RSTn
POWER_RSTn
NRST
Sys tem Res et
min 20 us
pulse generator
Backup domain reset
A backup domain reset is generated by setting the BKPRST bit in the backup domain control
register or backup domain power on reset (V
DD
or V
BAT
power on, if both supplies have
previously been powered off).
5.2.
Clock control unit (CCTL)
5.2.1.
Overview
The clock control unit provides a range of f requencies and clock f unctions. These include a
Internal 8M RC oscillator (IRC8M), a Internal 48M RC oscillator (IRC48M), a High Speed
crystal oscillator (HXTAL), a Low Speed Internal 40K RC oscillator (IRC40K), a Low Speed
crystal oscillator (LXTAL), three Phase Lock Loop (PLL), a HXTAL clock monitor, clock
prescalers, clock multiplexers and clock gating circuitry.
The clocks of the AHB, APB and Cortex
®
-M4 are derived f rom the system clock (CK_SYS)
which can source from the IRC8M, HXTAL or PLL. The maximum operating frequency of the
system clock (CK_SYS) can be up to 168 MHz.