Z8FMC16100 Datasheet, PDF (259/402 Pages) Zilog, Inc. – Z8 Encore-R Motor Control Flash MCUs

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 32 KHz to 20 MHz. In addition, the
oscillator can support ceramic resonators with oscillation frequencies up to 20 MHz. This
oscillator generates the primary system clock for the internal eZ8 CPU and the majority of
the on-chip peripherals. Alternatively, the X_IN input pin can also accept a CMOS-level
clock input signal (32 KHz–20 MHz). If an external clock generator is used, the X_OUT pin
must remain unconnected.
When configured for use with crystal oscillators or external clock drivers, the frequency of
the signal on the X_IN 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 20 MHz. Recommended 20 MHz crys-
tal specifications are provided in Table 132. The printed circuit board layout must add no
more than 4 pF of stray capacitance to either the X_IN or X_OUT pins. If oscillation does not
occur, reduce the values of capacitors C1 and C2 to decrease loading.
On-Chip Oscillator
X_IN
20 MHz Crystal
(Fundamental Mode)
X_OUT
C₂ = 22 pF
C₂ = 22 pF
Figure 40. Recommended 20MHz Crystal Oscillator Configuration
PS024604-1005
PRELIMINARY
Crystal Oscillator Operation