MC68HC908RF2 Datasheet, PDF (110/254 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Internal Clock Generator Module (ICG)
8.5.6
8.5.6.1
8.5.6.2
8.5.6.3
8.5.7
8.5.8
Nominal Frequency Settling Time . . . . . . . . . . . . . . . . . . . 131
Settling to Within 15 Percent . . . . . . . . . . . . . . . . . . . . . 131
Settling to Within 5 Percent . . . . . . . . . . . . . . . . . . . . . . 132
Total Settling Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Improving Settling Time . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Trimming Frequency on the Internal Clock Generator . . . . 135
8.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
8.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
8.7 Configuration Register Option . . . . . . . . . . . . . . . . . . . . . . . . 137
8.7.1 EXTSLOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
8.8 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
8.8.1 ICG Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
8.8.2 ICG Multiplier Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
8.8.3 ICG Trim Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.8.4 ICG DCO Divider Register . . . . . . . . . . . . . . . . . . . . . . . . . 145
8.8.5 ICG DCO Stage Register . . . . . . . . . . . . . . . . . . . . . . . . . . 146
8.2 Introduction
The internal clock generator module (ICG) is used to create a stable
clock source for the microcontroller without using any external
components. The ICG generates the oscillator output clock
(CGMXCLK), which is used by the COP, LVI, and other modules. The
ICG also generates the clock generator output (CGMOUT), which is fed
to the system integration module (SIM) to create the bus clocks. The bus
frequency will be one-fourth the frequency of CGMXCLK and one-half
the frequency of CGMOUT.
8.3 Features
Advance Information
110
The ICG has these features:
• External clock generator, either 1-pin external source or 2-pin
crystal
• Internal clock generator with programmable frequency output in
integer multiples of a nominal frequency (307.2 kHz ±25 percent)
Internal Clock Generator Module (ICG)
MC68HC908RF2 — Rev. 1
MOTOROLA