Datasheet

56F826 Technical Data, Rev. 14

28 Freescale Semiconductor

Figure 3-8 Flash Mass Erase Cycle

3.6 External Clock Operation

The 56F826 system clock can be derived from a crystal or an external system clock signal. To generate a

reference frequency using the internal oscillator, a reference crystal must be connected between the

EXTAL and XTAL pins.

3.6.1 Crystal Oscillator

The internal oscillator is also designed to interface with a parallel-resonant crystal resonator in the

frequency range specified for the external crystal in Table 3-9. A recommended crystal oscillator circuit

is shown in Figure 3-9. Follow the crystal supplier’s recommendations when selecting a crystal, because

crystal parameters determine the component values required to provide maximum stability and reliable

start-up. The crystal and associated components should be mounted as close as possible to the EXTAL

and XTAL pins to minimize output distortion and start-up stabilization time.The internal 56F82x

oscillator circuitry is designed to have no external load capacitors present. As shown in Figure 3-9, no

external load capacitors should be used.

The 56F80x components internally are modeled as a parallel resonant oscillator circuit to provide a

capacitive load on each of the oscillator pins (XTAL and EXTAL) of 10pF to 13pF over temperature and

process variations. Using a typical value of internal capacitance on these pins of 12pF and a value of 3pF

XADR

YE=SE=OE=0

ERASE

NVSTR

Tnvs

Tnvh1

Trcv

Tme

MAS1

IFREN