System Integration Module (SIM)
SIM Bus Clock Control and Generation
MC68HC908GP32
•
MC68HC08GP32
—
Rev. 6
Technical Data
MOTOROLA
System Integration Module (SIM)
281
19.3 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and
peripherals on the MCU. The system clocks are generated from an
incoming clock, CGMOUT, as shown in
Figure 19-3
. This clock can
come from either an external oscillator or from the on-chip PLL.
(See
Section 7. Clock Generator Module (CGMC)
.)
Figure 19-3. CGM Clock Signals
19.3.1 Bus Timing
In user mode
,
the internal bus frequency is either the crystal oscillator
output (CGMXCLK) divided by four or the PLL output (CGMVCLK)
divided by four.
19.3.2 Clock Startup from POR or LVI Reset
When the power-on reset module or the low-voltage inhibit module
generates a reset, the clocks to the CPU and peripherals are inactive
÷
2
BUS CLOCK
GENERATORS
SIM
SIM COUNTER
MONITOR MODE
USER MODE
SIMOSCEN
OSCILLATOR (OSC)
OSC2
OSC1
PHASE-LOCKED LOOP (PLL)
CGMXCLK
CGMRCLK
IT12
CGMOUT
SIMDIV2
PTC3
TO TIMTB15A, ADC
OSCSTOPENB
FROM
CONFIG
TO REST
OF CHIP
IT23
TO REST
OF CHIP
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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