CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U16846EJ1V0UD
84
5.3 Registers Controlling Clock Generator
The following seven registers are used to control the clock generator.
•
Processor clock control register (PCC)
•
Ring-OSC mode register (RCM)
•
Main clock mode register (MCM)
•
Main OSC control register (MOC)
•
Oscillation stabilization time counter status register (OSTC)
•
Oscillation stabilization time select register (OSTS)
•
System wait control register (VSWC)
(1) Processor clock control register (PCC)
This register sets the division ratio of the CPU clock.
PCC can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears this register to 00H.
Figure 5-2. Format of Processor Clock Control Register (PCC)
Address: FFFBH After reset: 00H R/W
Symbol
7 6 5 4 3 2 1 0
PCC
0 0 0 0 0
PCC2
PCC1
PCC0
CPU clock selection (f
CPU
)
PCC2 PCC1 PCC0
MCM0 = 0
MCM0 = 1
0 0 0
f
X
f
R
f
XP
0 0 1
f
X
/2 f
R
/2 f
XP
/2
0 1 0
f
X
/2
2
Setting
prohibited
f
XP
/2
2
0 1 1
f
X
/2
3
Setting
prohibited
f
XP
/2
3
1 0 0
f
X
/2
4
Setting
prohibited
f
XP
/2
4
Other than above
Setting prohibited
Remarks 1. MCM0: Bit 0 of the main clock mode register (MCM)
2. f
X
: Main system clock oscillation frequency (high-speed system clock oscillation frequency or Ring-
OSC clock oscillation frequency)
3. f
R
: Ring-OSC clock oscillation frequency
4. f
XP
: High-speed system clock oscillation frequency