SH7708 datasheet(194/633 Pages) RENESAS

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176

3. In clock modes 3 and 4, the SH7708 Series cannot go to standby mode while PLL

circuit 1 is on. Always set PSTBY and PLLEN to 0 to stop PLL circuit 1 before going

to standby mode.

4. When PSTBY and PLLEN are both changed from 0 to 1 together, the WDT will

automatically start counting and the clock will switch when the WDT overflows. See

section 9.5, Changing the Frequency, for setting the WDT.

PLL1

off

PLL1

standby

PSTBY = 1

(STC)

PSTBY = 0

(STC)

PLL1

PLLEN = 1

(IFC, PFC)

PSTBY = 1

and PLLEN = 1

PSTBY = 0, PLLEN = 0

(STC, IFC, PFC)

PSTBY = 0

and PLLEN = 0

PSTBY = 1

and PLLEN = 0

PLLEN = 0

(STC, IFC, PFC)

Note: Bits in parentheses can be changed simultaneously.

Figure 9.3 State Transitions for the PLL Standby Function

9.7

Controlling Clock Output

The CKOEN bit in the FRQCR register can be used to switch between outputting a clock to the

CKIO pin or having the level fixed.

9.7.1

Clock Modes 0–2

The CKIO pin level cannot be fixed. Always set the CKOEN bit in FRQCR to 1 (clock output).

9.7.2

Clock Modes 3 and 4

The CKIO output changes as soon as the CKOEN bit is changed. When the WDT is started by

simultaneously changing the multiplication rate of PLL circuit 1 or switching PLL circuit 1 on or

off, the WDT starts running after the CKIO output is switched, and then the internal clock

changes.

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