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Clock Generator
Chapter 4
Preliminary User’s Manual U17566EE1V2UM00
5.
Make sure that all DMA channels are disabled. Otherwise a DMA could
happen between steps 7 and 8, and the power down mode may not be
entered at all.
Further on do not perform write operations to PRCMD and write-protected
registers by DMA transfers.
6.
No special sequence is required for reading the PSC register.
Caution
If a wake-up event occurs within the 5 “nop” instructions after a power save
mode request (PSC.STP = 1) the microcontroller is immediately returning from
power save mode, but may have not at all or only partly entered the power
save mode. Following three situations can occur:
1. power save mode request not accepted
wake-up configuration not established, PLL/SSCG are operating
2. power save mode request accepted, but not completed
wake-up configuration established, but PLL/SSCG operating
3. power save mode request accepted and completed
wake-up configuration established, PLL/SSCG stopped
4.3.4
CPU operation after power save mode release
Clock Generator re-
configuration
The clock for the CPU system can be switched only once after reset or power
save mode release.
The clocks for the Watchdog Timer, Watch Timer, and LCD Controller/Driver
can be switched only once after system reset.
Access to peripherals that have no clock supply in Sub-WATCH mode may
cause system deadlock. This can happen if the main oscillator remains
disabled.
Wake-up
configuration
Wake-up configuration established means that all registers and clock paths are
set to their wake-up state.
The software should check after wake-up whether the expected wake-up
configuration has been completely established. This can be achieved by
observing
• following clock generator registers, which are modified by power save mode
entry and wake-up
– after WATCH, Sub-WATCH, STOP wake-up following bits are cleared:
CKC.PLLEN, CKC.SCEN, CKC.PERIC, SCC.SEL, ICC.SEL
– after IDLE or STOP wake-up following bits are cleared:
PCC.CLS, PCC.CKS
– after Sub-WATCH or WATCH wake-up
PCC.CLS/PCC.CKS = 000
B
, if PSM.OSCDIS = 0
PCC.CLS/PCC.CKS = 100
B
, if PSM.OSCDIS = 1
• the “completed power save mode” bit CGSTAT.CMPLPSM
– CGSTAT.CMPLPSM = 0 if a power save mode request has been
accepted but not completed, wake-up configuration established, but PLL/
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