MC68HC908GT16 Datasheet, PDF (114/412 Pages) Motorola, Inc – Microcontrollers

Internal Clock Generator (ICG) Module
7.4.2 Internal Clock Generator
The internal clock generator, shown in Figure 7-2, creates a low
frequency base clock (IBASE), which operates at a nominal frequency
(f_NOM) of 307.2 kHz ± 25 percent, and an internal clock (ICLK) which is
an integer multiple of IBASE. This multiple is the ICG multiplier factor
(N), which is programmed in the ICG multiplier register (ICGMR). The
internal clock generator is turned off and the output clocks (IBASE and
ICLK) are held low when the internal clock generator enable signal
(ICGEN) is clear.
The internal clock generator contains:
• A digitally controlled oscillator
• A modulo N divider
• A frequency comparator, which contains voltage and current
references, a frequency to voltage converter, and comparators
• A digital loop filter
ICGEN
VOLTAGE AND
++
CURRENT
REFERENCES
+
DIGITAL
LOOP
FILTER
–
––
TRIM[7:0]
DIGITALLY
CONTROLLED
OSCILLATOR
N[6:0]
FICGS
DSTG[7:0]
DDIV[3:0]
ICLK
FREQUENCY
COMPARATOR
CLOCK GENERATOR
NAME
NAME
CONFIG2 REGISTER BIT
TOP LEVEL SIGNAL
MODULO
N
DIVIDER
NAME
NAME
IBASE
REGISTER BIT
MODULE SIGNAL
Figure 7-2. Internal Clock Generator Block Diagram
Technical Data
114
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
Internal Clock Generator (ICG) Module
MOTOROLA