HD64F2149 Datasheet, PDF (760/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

24.6.3 Setting Oscillation Settling Time after Clearing Software Standby Mode
Bits STS2 to STS0 in SBYCR should be set as described below.
Using a Crystal Oscillator: Set bits STS2 to STS0 so that the standby time is at least 8 ms (the
oscillation settling time).
Table 24.5 shows the standby times for different operating frequencies and settings of bits STS2 to
STS0.
Table 24.5 Oscillation Settling Time Settings
STS2 STS1 STS0 Standby Time
0
0
0
8192 states
10 MHz 8 MHz 6 MHz 4 MHz 2 MHz Unit
0.8
1.0
1.3
2.0
4.1
ms
1
16384 states
1.6
2.0
2.7
4.1
8.2
1
0
32768 states
3.3
4.1
5.5
8.2 16.4
1
65536 states
6.6
8.2 10.9 16.4 32.8
1
0
0
131072 states
13.1 16.4 21.8 32.8 65.5
1
262144 states 26.2 32.8 43.6 65.6 131.2
1
0
Reserved
—
—
—
—
—
µs
1
16 states*
1.6
2.0
2.7
4.0
8.0
: Recommended time setting
Notes: * The maximum operating frequency for the H8S/2169 and H8S/2149 is 10 MHz.
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.
24.6.4 Software Standby Mode Application Example
Figure 24.3 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.
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