CHAPTER 5 CLOCK GENERATORS
User’s Manual U16898EJ3V0UD
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5.3 Registers Controlling Clock Generators
The clock generators are controlled by the following four registers.
•
Processor clock control register (PCC)
•
Preprocessor clock control register (PPCC)
•
Low-speed internal oscillation mode register (LSRCM)
•
Oscillation stabilization time select register (OSTS)
(1) Processor clock control register (PCC) and preprocessor clock control register (PPCC)
These registers are used to specify the division ratio of the system clock.
PCC and PPCC are set by using a 1-bit or 8-bit memory manipulation instruction.
Reset signal generation sets PCC and PPCC to 02H.
Figure 5-2. Format of Processor Clock Control Register (PCC)
Address: FFFBH After reset: 02H R/W
Symbol
7 6 5 4 3 2 1 0
PCC 0 0 0 0 0 0
PCC1
0
Figure 5-3. Format of Preprocessor Clock Control Register (PPCC)
Address: FFF3H After reset: 02H R/W
Symbol
7 6 5 4 3 2 1 0
PPCC 0 0 0 0 0 0
PPCC1
PPCC0
PPCC1
PPCC0
PCC1
Selection of CPU clock (f
CPU
)
0 0 0
f
X
0 1 0
f
X
/2
Note 1
0 0 1
f
X
/2
2
1 0 0
f
X
/2
2
Note 2
0 1 1
f
X
/2
3
Note 1
1 0 1
f
X
/2
4
Note 2
Other than above
Setting prohibited
Notes 1.
If PPCC = 01H, the clock (f
XP
) supplied to the peripheral hardware is f
X
/2.
2.
If PPCC = 02H, the clock (f
XP
) supplied to the peripheral hardware is f
X
/2
2
.
