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MOTOROLA
MC68328 DRAGONBALL PROCESSOR USER’S MANUAL
3-1
SECTION 3
PHASE-LOCKED LOOP AND POWER CONTROL
The phase-locked-loop (PLL) block generates all clocks for the MC68328 processor. It
includes a crystal oscillator for use with low-frequency (32.768 kHz) crystals. The PLL gen-
erates a high-frequency master clock phase-locked to the crystal reference.
3.1 OVERVIEW
The PLL is a flexible clock source for the MC68328. It provides a crystal-controlled master
clock at frequencies from 10MHz to the maximum operational frequency in 32-kHz steps.
The master clock can be divided to provide a system clock as low as 1/16th of the voltage-
controlled oscillator (VCO) frequency. The low-frequency reference clock (32.768 kHz or
38.4 kHz) is always available to the real-time clock or timer. The PLL can be disabled to save
power, but it can be re-enabled within 2 ms of a wake-up interrupt. This block, in conjunction
with the power-control block, provides an efficient power-control mechanism for the
MC68328 processor (see Figure 3-1 below).
3.2 PROGRAMMER’S MODEL
The PLL has three registers that provide complete control and status information. Descrip-
tions of these registers follow.
Figure 3-1. PLL Block Diagram
MPU Interface
Crystal
WAKEUP
MPU BUS
Oscillator
Phase Locked
Loop
Divider
CLK32
SYSCLK
EXTAL
XTAL
PIXCLK
Summary of Contents for DragonBall MC68328
Page 5: ...vi MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 25: ...Overview 1 14 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 45: ...System Integration Module 2 20 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 103: ...Parallel Ports 7 16 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 117: ...UART 8 14 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 127: ...SPI Master 10 6 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...