4552 Datasheet, PDF (57/145 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4552 Group
CLOCK CONTROL
The clock control circuit consists of the following circuits.
• On-chip oscillator (internal oscillator)
• Ceramic resonator
• RC oscillation circuit
• Quartz-crystal oscillation circuit
• Multi-plexer (clock selection circuit)
• Frequency divider
• Internal clock generating circuit
The system clock and the instruction clock are generated as the
source clock for operation by these circuits.
Figure 47 shows the structure of the clock control circuit.
The 4552 Group operates by the on-chip oscillator clock (f(RING))
which is the internal oscillator after system is released from reset.
Also, the ceramic resonator or the RC oscillation can be used for
the main clock (f(XIN)) of the 4552 Group.
The quartz-crystal oscillator can be used for sub-clock (f(XCIN)).
On-chip oscillator
(internal oscillator)
XIN
XOUT
XCIN
XCOUT
Ceramic
resonance
RC oscillation
Quartz-crystal
oscillation
MR1, MR0
00
01
10
Division circuit
Divided by 8
Divided by 4
Divided by 2
MR3, MR2
11
10
01
00
RG0
System clock (STCK)
Internal clock
generating circuit
(divided by 3)
Instruction clock
(INSTCK)
Multi-
plexer
QS
CRCK instruction
RG1
QR
QS
R
EPOF instruction ⁺
Internal reset signal
T3F signal
Key-on wakeup signal
POF instruction
QS
RG2
R
EPOF instruction + POF2 instruction
Fig. 47 Clock control circuit structure
Rev.3.02 Dec 22, 2006 page 57 of 142
REJ03B0023-0302