Rainbow Electronics W90N740 - Manual (Page 38)

W90N740
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WDT [8] ： WDT clock enable bit
0 = Disable WDT counting clock
1 = Enable WDT counting clock
USB [7] ： USB clock enable bit
0 = Disable USB clock
1 = Enable USB clock
TIMER [6] ： Timer clock enable bit
0 = Disable Timer clock
1 = Enable Timer clock
UART [5] ： UART clock enable bit
0 = Disable UART clock
1 = Enable UART clock
ECLKS [4] ： External clock select
0 = External clock from EXTAL pin is used as system clock
1 = PLL output clock is used as system clock
After power on reset, the content of ECLKS is the Power-On Setting value. You can program this bit to
change the system clock source.
CLKS [3:1] ： PLL output clock select
CLKS [3:1] PLL output clock
0 0 0 58.594 KHz*
0 0 1 24 MHz
0 1 0 48 MHz
0 1 1 60 MHz
1 0 0 80 MHz
1 0 1 RESERVED
1 1 0 RESERVED
1 1 1 RESERVED
When 24Mhz ~ 120MHz is setting, the ECLKS bit is needed to set on PLL output clock mode (logic 1).
*About 58.594KHz setting, two steps are needed.
First step, the ECLKS bit is set to External Clock mode (logic 0, 15MHz), then set CLKS bits to 0.