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Chapter 4
Clock Generator
Preliminary User’s Manual U17566EE1V2UM00
Table 4-18
PSM register contents
Bit position
Bit name
Function
6
CMODE
Watch Calibration Timer clock selection:
0: PCLK1.
1: Main oscillator.
3
OSCDIS
Main oscillator disable/enable control during and after power save mode:
0: Main oscillator enabled.
1: Main oscillator disabled.
Caution:
If OSCDIS is set to 1, the main oscillator clock supply for the Watch
Timer and the LCD Controller/Driver are stopped immediately.
Thus these function stop their operation immediately as well, when the
main oscillator is used as the clock source.
OSCDIS determines also the behaviour of the main oscillator during and after
power save mode. The effect of this bit differs, depending on the power save mode.
•
Sub-WATCH mode
During Sub-WATCH mode the main oscillator is always stopped. OSCDIS
determines whether the main oscillator shall be started and chosen as CPU clock
source or should remain stopped after Sub-WATCH mode release.
0: Main oscillator enable.
The main oscillator is started after Sub-WATCH mode release and the CPU is
supplied with the main oscillator clock, after the oscillation stabilization time has
elapsed.
1: Main oscillator disable.
The main oscillator remains stopped after Sub-WATCH release.
The CPU is supplied with the selected sub clock—either sub oscillator or ring
oscillator (see bit PCC.SOSCP).
Since the reset value of OSCDIS is 1 and PCC.SOSCP is 0 the CPU starts
always with the ring oscillator clock after reset release.
In both cases, the application software must start the main oscillator by clearing
the OSCDIS bit. After the oscillator stabilization time has elapsed (see bit
CGSTAT.OSCSTAT), the main oscillator can be used as system clock source by
setting the PCC register accordingly.
•
WATCH mode
This bit determines whether the main oscillator shall be stopped or remain in
operation during WATCH mode. In either case after WATCH mode release the CPU
is operating on the main oscillator.
0: Main oscillator enable.
The main oscillator is operating during WATCH mode.
After WATCH mode release the CPU is supplied with the main oscillator clock.
1: Main oscillator disable.
The main oscillator is stopped during WATCH mode.
After WATCH mode release the main oscillator is started and the CPU is
supplied with the main oscillator clock, after the oscillation stabilization time has
elapsed.
1 to 0
PSM[1:0]
Power save mode selection:
PSM1
PSM0
Power save mode
0
0
IDLE
0
1
STOP
1
0
WATCH
1
1
Sub-WATCH mode (main oscillator shut down)
It is not possible to switch to IDLE or WATCH mode when the CPU is operated by a
sub clock. If IDLE or WATCH mode is selected during sub clock operation, the Sub-
WATCH mode will be entered.
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