s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 120

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

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