Datasheet

MC68HC908QYA/QTA Family Data Sheet, Rev. 3
Freescale Semiconductor 193
A.2.2 Enhanced Oscillator Module (OSC)
The QYxA contains a much enhanced oscillator module that allows more options than the QYx Classic.
• The ICFS bits in the Oscillator Status and Control Register (OSCSC) allow the Internal Oscillator
to be configured for 1-, 2-, or 3.2-MHz operation. Also, the ECFS bits in the same register allow a
low, medium, or high crystal frequency range to be selected for the source of the system clock.
With this option you can choose to use a 32-kHz (low range) or a 16-MHz (high range) crystal.
• Another improvement to the Oscillator Module design is that you can switch between internal
oscillator and external oscillator options at any time. For example, if you wanted the low power
advantage of running from a 32-kHz crystal but still needed some processing power to perform
math calculations you could switch back and forth between internal and external clock. The same
is true for switching between 1-, 2-, and 3.2-MHz internal oscillator options.
A.2.2.1 Registers Affected
The OSCOPT bits are no longer in the CONFIG2 register and now reside in the OSCSC register. Also,
the ICFSx and ECFSx bits now reside in this register.
The IFS bits are used to select different Internal Oscillator speeds.
The ECFS bits are used to select the range of crystal that should be used to provide the reference clock.
Bit 7654321Bit 0
Read:
OSCOPT1 OSCOPT0 ICFS1 ICFS0 ECFS1 ECFS0 ECGON
ECGST
Write:
Reset:00100000
= Unimplemented
Figure A-4. Oscillator Status and Control Register (OSCSC)