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Section 4 Clock Pulse Generator (CPG)
Rev. 4.00 Sep. 14, 2005 Page 151 of 982
REJ09B0023-0400
4.5
Changing the Frequency
The frequency of the internal clock and peripheral clock can be changed either by changing the
multiplication rate of PLL circuit 1 or by changing the division rates of divider. All of these are
controlled by software through the frequency control register. The methods are described below.
4.5.1
Changing the Multiplication Rate
A PLL settling time is required when the multiplication rate of PLL circuit 1 is changed. The on-
chip WDT counts the settling time.
1. In the initial state, the multiplication rate of PLL circuit 1 is 1.
2. Set a value that will become the specified oscillation settling time in the WDT and stop the
WDT. The following must be set:
WTCSR register TME bit
=
0: WDT stops
WTCSR register CKS2 to CKS0 bits: Division ratio of WDT count clock
WTCNT counter: Initial counter value
3. Set the desired value in the STC1 and STC0 bits. The division ratio can also be set in the
IFC[1:0] and PFC[1:0] bits.
4. The processor pauses temporarily and the WDT starts incrementing. The internal and
peripheral clocks both stop and the WDT is supplied with the clock. The clock will continue to
be output at the CKIO pin. This state is the same as the standby state. Whether or not registers
are initialized depends on the module. For details, see table 6.3, Register States in Standby
Mode in section 6, Power-Down Modes.
5. Supply of the clock that has been set begins at WDT count overflow, and the processor begins
operating again. The WDT stops after it overflows.
4.5.2
Changing the Division Ratio
Counting by the WDT does not proceed if the frequency divisor is changed but the multiplier is
not.
1. In the initial state, IFC[1:0]
=
B'00 and PFC[1:0]
=
B'11
2. Set the desired value in the IFC[1:0] and PFC[1:0] bits. The values that can be set are limited
by the clock mode and the multiplication rate of PLL circuit 1. Note that if the wrong value is
set, the processor will malfunction.
3. The clock is immediately supplied at the new division ratio.
Summary of Contents for HD6417641
Page 2: ...Rev 4 00 Sep 14 2005 Page ii of l...
Page 7: ...Rev 4 00 Sep 14 2005 Page vii of l...
Page 11: ...Rev 4 00 Sep 14 2005 Page xi of l USB Universal serial bus WDT Watch dog timer...
Page 12: ...Rev 4 00 Sep 14 2005 Page xii of l...
Page 28: ...Rev 4 00 Sep 14 2005 Page xxviii of l...
Page 204: ...Section 4 Clock Pulse Generator CPG Rev 4 00 Sep 14 2005 Page 154 of 982 REJ09B0023 0400...
Page 212: ...Section 5 Watchdog Timer WDT Rev 4 00 Sep 14 2005 Page 162 of 982 REJ09B0023 0400...
Page 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Page 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Page 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Page 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Page 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Page 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Page 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Page 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Page 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Page 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Page 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
Page 1032: ...Rev 4 00 Sep 14 2005 Page 982 of 982 REJ09B0023 0400 X X Y data addressing 52 X Y memory 193...
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