mc68hc908rf2 Freescale Semiconductor, Inc, mc68hc908rf2 Datasheet - Page 67

• Manufacturer Part Number: mc68hc908rf2
• Description: M68hc08 Microcontrollers Microcontroller / Transmitter
• Manufacturer: Freescale Semiconductor, Inc

6.3.1 Clock Enable Circuit
6.3.2 Internal Clock Generator
MC68HC908RF2 — Rev. 4.0
MOTOROLA
REFERENCES
ICGEN
VOLTAGE &
CURRENT
The clock enable circuit is used to enable the internal clock (ICLK) or external clock
(ECLK). The clock enable circuit generates an ICG stop (ICGSTOP) signal which
stops all clocks (ICLK, ECLK, and the low-frequency base clock, IBASE) low.
ICGSTOP is set and the ICG is disabled in stop mode.
The internal clock enable signal (ICGEN) turns on the internal clock generator
which generates ICLK. ICGEN is set (active) whenever the ICGON bit is set and
the ICGSTOP signal is clear. When ICGEN is clear, ICLK and IBASE are both low.
The external clock enable signal (ECGEN) turns on the external clock generator
which generates ECLK. ECGEN is set (active) whenever the ECGON bit is set and
the ICGSTOP signal is clear. When ECGEN is clear, ECLK is low.
The internal clock generator, shown in
clock (IBASE), which operates at a nominal frequency (f
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.
Figure 6-2. Internal Clock Generator Block Diagram
Freescale Semiconductor, Inc.
– –
For More Information On This Product,
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++
+
Internal Clock Generator Module (ICG)
Go to: www.freescale.com
CLOCK GENERATOR
COMPARATOR
FREQUENCY
TRIM[7:0]
DIGITAL
FILTER
LOOP
Figure
CONTROLLED
OSCILLATOR
DIGITALLY
NAME
NAME
MODULO
DIVIDER
N[6:0]
Internal Clock Generator Module (ICG)
6-2, creates a low-frequency base
N
MODULE SIGNAL
REGISTER BIT
NOM
) of 307.2 kHz ±25
Functional Description
DSTG[7:0]
DDIV[3:0]
IBASE
ICLK
Data Sheet
67