ZUSBOPTSC01ZAC datasheet(259/402 Pages) ZILOG

259 / 402 page

PS024604-1005

P R E L I M I N A R Y

Crystal Oscillator Operation

Z8FMC16100 Series Flash MCU

Product Specification

237

On-Chip Oscillator

The products in the Z8FMC16100 Series Flash MCU features an on-chip oscillator for use

with external crystals with frequencies ranging from 32KHz to 20MHz. In addition, the

oscillator can support ceramic resonators with oscillation frequencies up to 20MHz. This

oscillator generates the primary system clock for the internal eZ8 CPU and the majority of

the on-chip peripherals. Alternatively, the XIN input pin can also accept a CMOS-level

clock input signal (32KHz–20MHz). If an external clock generator is used, the XOUT pin

must remain unconnected.

When configured for use with crystal oscillators or external clock drivers, the frequency of

the signal on the XIN input pin determines the frequency of the system clock (that is, no

internal clock divider).

Crystal Oscillator Operation

Figure 40 illustrates a recommended configuration for connection with an external funda-

mental-mode, parallel-resonant crystal operating at 20MHz. Recommended 20MHz crys-

tal specifications are provided in Table 132. The printed circuit board layout must add no

more than 4pF of stray capacitance to either the XIN or XOUT pins. If oscillation does not

occur, reduce the values of capacitors C1 and C2 to decrease loading.

Figure 40. Recommended 20MHz Crystal Oscillator Configuration

C = 22 pF

XOUT

C = 22 pF

20 MHz Crystal

(Fundamental Mode)

On-Chip Oscillator

ZUSBOPTSC01ZAC 数据表(PDF) 259 Page - Zilog, Inc.