Eurotech BRI ISDN Manual do Utilizador descarregar pdf (Página 24)

Am186

CC Microcontroller ISDN TA Reference Design Manual

2-6

The system uses a single 24-MHz crystal. This design uses an internal 2x PLL

which provides a 48-MHz system clock and the required 48-MHz USB clock.

Because the USB clock is derived from the system PLL, the USB crystal input,

USBX1, is terminated. The clock generation circuit is shown in Figure 2-3.

Figure 2-3. ISDN TA Clock Generation Circuit

24.000 MHz

C57

27pF

C58

27pF

R33

10K

USBX1

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Eurotech BRI ISDN Manual do Utilizador Página 24