Datasheet

Section 25 Power-Down State
Rev. 4.00 Sep 27, 2006 page 758 of 1130
REJ09B0327-0400
Using a Crystal Oscillator
Set bits STS2 to STS0 so that the standby time is at least 8 ms (the oscillation settling time).
Table 25.5 shows the standby times for different operating frequencies and settings of bits STS2 to
STS0.
Table 25.5 Oscillation Settling Time Settings
STS2 STS1 STS0 Standby Time
20
MHz
16
MHz
12
MHz
10
MHz
8
MHz
6
MHz
4
MHz
2
MHz Unit
0 0 0 8192 states 0.41 0.51 0.65 0.8 1.0 1.3 2.0 4.1 ms
1 16384 states 0.82 1.0 1.3 1.6 2.0 2.7 4.1 8.2
1 0 32768 states 1.6 2.0 2.7 3.3 4.1 5.5 8.2 16.4
1 65536 states 3.3 4.1 5.5 6.6 8.2 10.9 16.4 32.8
1 0 0 131072 states 6.6 8.2 10.9 13.1 16.4 21.8 32.8 65.5
1 262144 states 13.1 16.4 21.8 26.2 32.8 43.6 65.6 131.2
10Reserved ———————— µs
1 16 states
*
0.8 1.0 1.3 1.6 2.0 2.7 4.0 8.0
: Recommended time setting
Note: * This setting must not be used in the flash memory version.
Using an External Clock
Any value can be set. Normally, use of the minimum time is recommended.
25.6.4 Software Standby Mode Application Example
Figure 25.3 shows an example in which a transition is made to software standby mode at the
falling edge on the NMI pin, and software standby mode is cleared at the rising edge on the NMI
pin.
In this example, an NMI interrupt is accepted with the NMIEG bit in SYSCR cleared to 0 (falling
edge specification), then the NMIEG bit is set to 1 (rising edge specification), the SSBY bit is set
to 1, and a SLEEP instruction is executed, causing a transition to software standby mode.
Software standby mode is then cleared at the rising edge on the NMI pin.