Semiconductor Group
9-7
1997-10-01
Power Saving Modes
C541U
9.2.2 Exit from Power Down Mode
If the power down mode is exit via a hardware reset, the microcontroller with its SFRs is put into the
hardware reset state and the content of RAM and XRAM are not changed. The reset signal that
terminates the power down mode also restarts the RC oscillator and the on-chip oscillatror. The
reset operation should not be activated before
V
DD
is
restored
to
its
normal
operating level and
must be held active long enough to allow the oscillator to restart and stabilize (similar to power-on
reset). The USB clock system must be cotrolled as described for the hardware reset in chapter 5.
Figure 9-1 shows the procedure which must is executed when the power down mode is left via the
wake-up capability.
Figure 9-1
Wake-up from Power Down Mode Procedure
Invalid Address / Data
Invalid Address
00H
7BH
1st Instr. of ISR
P0
P2
PSEN
ALE
P3.2 / INT0
or
Activity Detected
on USB Bus
10
µ
s
min.
Power Down
Mode
Latch
Phase
typ. 5 ms
Watchdog Circuit
Oscillator Start-Up Phase
1)
2)
3)
4)
5)
Execution of
Interrupt at
007B
H
RETI
Instruction
Detailed Timing of Beginning of Phase 4
MCT03418
Содержание C541U
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