H8SSLASH2218 datasheet(668/750 Pages) RENESAS

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Section 20 Power-Down Modes

Rev.6.00 Jun. 03, 2008 Page 620 of 698

REJ09B0074-0600

20.4.3

Setting Oscillation Stabilization 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 tOSC2 ms (the oscillation stabilization

time).

Table 20.3 shows the standby times for different operating frequencies and settings of bits

STS2 to STS0.

• Using an External Clock

Set bits STS2 to STS0 as any value. Usually, minimum value is recommended. A standby time

of 100

μs or longer (flash memory power supply stabilization time) should be used in the F-

ZTAT version.

Table 20.3

Oscillation Stabilization Time Settings

STS2 STS1

STS0

Standby Time

24MHz 20MHz 16MHz 13MHz 10MHz 8MHz

6MHz

4MHz

2MHz

Unit

8192 states

0.34

0.41

0.51

0.63

0.82

1.0

1.4

2.0

4.1

16384 states

0.68

0.82

1.0

1.3

1.6

2.0

2.7

4.1

8.2

32768 states

1.4

1.6

2.0

2.5

3.3

4.1

5.5

8.2

16.4

65536 states

2.7

3.3

4.1

5.0

6.6

8.2

10.9

16.4

32.8

131072 states

5.5

6.6

8.2

10.1

13.1

16.4

21.8

32.8

65.5

262144 states

10.9

13.1

16.4

20.2

26.2

32.8

43.7

65.5

131.1

2048 states

0.09

0.10

0.13

0.16

0.20

0.26

0.34

0.51

1.0

16 states

0.67

0.80

1.0

1.2

1.6

2.0

2.7

4.0

8.0

µs

: Recommended time setting (For conditions, see t

OSC2 in table 22.4.)

20.4.4

Software Standby Mode Application Example

Figure 20.4 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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