MC68HC908LB8_05 Datasheet, PDF (129/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Low Power Modes
13.4.6 Internal Oscillator Clock (INTCLK)
INTCLK is the internal oscillator output signal. Its nominal frequency is fixed to 16 MHz, but it can be also
trimmed using the oscillator trimming feature of the OSCTRIM register (see 13.3.1.1 Internal Oscillator
Trimming).
13.4.7 Oscillator Out 2 (BUSCLKX4)
BUSCLKX4 is the same as the input clock (XTALCLK, RCCLK, or INTCLK). This signal is driven to the
SIM module and is used to determine the COP cycles.
13.4.8 Oscillator Out (BUSCLKX2)
The frequency of this signal is equal to half of the BUSCLKX4, this signal is driven to the SIM for
generation of the bus clocks used by the CPU and other modules on the MCU. BUSCLKX2 will be divided
again in the SIM and results in the internal bus frequency being one fourth of either the XTALCLK,
RCCLK, or INTCLK frequency.
13.5 Low Power Modes
The WAIT and STOP instructions put the MCU in low-power consumption standby modes.
13.5.1 Wait Mode
The WAIT instruction has no effect on the oscillator logic. BUSCLKX2 and BUSCLKX4 continue to drive
to the SIM module.
13.5.2 Stop Mode
The STOP instruction disables either the XTALCLK, the RCCLK, or INTCLK output, hence BUSCLKX2
and BUSCLKX4.
13.6 Oscillator During Break Mode
The oscillator continues to drive BUSCLKX2 and BUSCLKX4 when the device enters the break state.
13.7 CONFIG2 Options
Two CONFIG2 register options affect the operation of the oscillator module: OSCOPT1 and OSCOPT0.
All CONFIG2 register bits will have a default configuration. Refer to Chapter 5 Configuration Register
(CONFIG) for more information on how the CONFIG2 register is used.
Table 13-2 shows how the OSCOPT bits are used to select the oscillator clock source.
MC68HC908LB8 Data Sheet, Rev. 1
Freescale Semiconductor
129