CHAPTER 5 CLOCK GENERATOR
User’s Manual U16899EJ2V0UD
112
Figure 5-2. Format of Processor Clock Control Register (PCC)
Address: FFFBH After reset: 00H R/W
Note 1
Symbol
<7> <6> <5> <4> 3
2
1
0
PCC MCC FRC CLS CSS 0 PCC2
PCC1
PCC0
MCC
Control of high-speed system clock oscillator operation
Note 2
0
Oscillation
possible
1
Oscillation
stopped
FRC
Subsystem clock feedback resistor selection
Note 3
0
On-chip feedback resistor used
1
On-chip feedback resistor not used
CLS
CPU
clock
status
0
High-speed system clock or Ring-OSC clock
1
Subsystem
clock
Notes 1. Bit 5 is read-only.
2. When the CPU is operating on the subsystem clock, MCC should be used to stop the high-speed
system clock oscillator operation. When the CPU is operating on the Ring-OSC clock, use bit 7
(MSTOP) of the main OSC control register (MOC) to stop the high-speed system clock oscillator
operation (this cannot be set by MCC). A STOP instruction should not be used.
3. Clear this bit to 0 when the subsystem clock is used, and set it to 1 when the subsystem clock is not
used.
4. Be sure to switch CSS from 1 to 0 when bits 1 (MCS) and 0 (MCM0) of the main clock mode register
(MCM) are 1.
Caution Be sure to clear bit 3 to 0.
CPU clock (f
CPU
) selection
CSS
Note 4
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
0
1 0 0
f
X
/2
4
Setting
prohibited
f
XP
/2
4
0
0
0
0
0
1
0
1
0
0
1
1
1
1 0 0
f
XT
/2
Other than above
Setting prohibited