mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 91

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

7.3 SIM Bus Clock Control and Generation
7.3.1 Bus Timing
7.3.2 Clock Start-Up from POR
7.3.3 Clocks in Stop Mode and Wait Mode
MC68HC908BD48
Freescale Semiconductor
From
SIM
SIMOSCEN
—
Rev. 2.1
OSC1
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, OSCOUT, as shown in
In user mode, the internal bus frequency is the oscillator frequency
(OSCXCLK) divided by four.
When the power-on reset module generates a reset, the clocks to the
CPU and peripherals are inactive and held in an inactive phase until after
the 4096 OSCXCLK cycle POR timeout has completed. The RST is
driven low by the SIM during this entire period. The IBUS clocks start
upon completion of the timeout.
Upon exit from stop mode (by an interrupt, break, or reset), the SIM
allows OSCXCLK to clock the SIM counter. The CPU and peripheral
clocks do not become active until after the stop delay timeout. This
timeout is selectable as 4096 or 32 OSCXCLK cycles. (See
Mode.)
Figure 7-2. OSC Clock Signals
System Integration Module (SIM)
OSC2
OSCILLATOR
÷ 2
OSCXCLK
OSCOUT
Figure
System Integration Module (SIM)
÷ 2
SIM COUNTER
7-2.
SIM
GENERATORS
BUS CLOCK
7.7.2 Stop
Data Sheet
91