MC68HC908QC16_07 Datasheet, PDF (120/274 Pages) Freescale Semiconductor, Inc – Microcontrollers

Periodic Wakeup Module (PWU)
PWUON — Periodic Wakeup Enabled Bit
This read/write bit enables or disables the periodic wakeup module.
1 = Periodic wakeup module is enabled.
0 = Periodic wakeup module is disabled.
PWUCLKSEL — Periodic Wakeup Clock Select Bit
This read/write bit selects the clock source for the prescaler.
1 = BUSCLKX4 is selected as the clock source for the prescaler.
0 = The internal 32 kHz RC oscillator is selected as the clock source for the prescaler.
NOTE
The PWUCLKSEL bit can only be written to when PWUON is clear.
PWUF — Periodic Wakeup Flag Bit
This read-only bit is set when the counter reaches the modulo value programmed in the PWUMOD
register. This bit is cleared by writing a 1 to the PWUACK bit or by a PWU interrupt vector fetch.
1 = Periodic wakeup interrupt pending
0 = No periodic wakeup interrupt pending.
PWUACK — Periodic Wakeup Acknowledge Bit
Writing a 1 to this write-only bit clears the PWUF. PWUACK always reads as 0.
PWUIE — Periodic Wakeup Interrupt Enable Bit
This read/write bit enables periodic wakeup interrupt requests.
1 = Periodic wakeup interrupt requests enabled.
0 = Periodic wakeup interrupt requests disabled.
SMODE — Periodic Wakeup Module Enabled in Stop Mode Bit
This read/write bit is used to allow the PWU module to continue running in stop mode.
1 = Periodic wakeup module continues to run in stop mode.
0 = Periodic wakeup module disabled in stop mode.
12.8.2 Periodic Wakeup Prescaler Register
The PWUP register is used to select the clock rate that will be input to the PWU counter. The prescaler
generates sixteen clock rates from either the dedicated low-power internal oscillator or from the bus clock
source (BUSCLKX4).
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
PS3
PS2
PS1
PS0
0
0
0
0
0
1
0
0
= Unimplemented
Figure 12-3. Periodic Wakeup Prescaler Register (PWUP)
PS3–PS0 — Prescaler Select Bits
These read/write bits select one of the sixteen prescaler outputs to be the input to the PWU counter.
NOTE
The PWUP register can only be written to when PWUON is clear.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 3
120
Freescale Semiconductor