mc68hc08ln56 Freescale Semiconductor, Inc, mc68hc08ln56 Datasheet - Page 63

• Manufacturer Part Number: mc68hc08ln56
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

5.2 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
come from either an external oscillator or from the on-chip PLL. (See
(CGMB).)
5.2.1 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. (See
5.2.2 Clock Start-Up 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 and held in an inactive phase until after the 4096 CGMXCLK cycle POR
timeout has completed. The RST pin is driven low by the SIM during this entire period. The IBUS clocks
start upon completion of the timeout.
5.2.3 Clocks in Stop Mode and Wait Mode
Upon exit from stop mode by an interrupt, break, or reset, the SIM allows CGMXCLK 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 CGMXCLK cycles. (See
In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
Freescale Semiconductor
OSC1
PLL
MC68HC08LN56 • MC68HC708LN56 General Release Specification, Rev. 2.1
CGMVCLK
MONITOR MODE
SELECT
CIRCUIT
CLOCK
USER MODE
BCS
CGM
PTC3
Figure 5-3. CGM Clock Signals
÷
2
A
B S*
Chapter 8 External Interrupt Module
*When S = 1,
CGMOUT = B
CGMXCLK
CGMOUT
5.6.2 Stop
Chapter 4 Clock Generator Module
SIM Bus Clock Control and Generation
Mode.)
Figure
÷
SIM COUNTER
2
SIM
5-3. This clock can
GENERATORS
BUS CLOCK
(IRQ).)
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