4559 Datasheet, PDF (61/148 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4559 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 59 shows the structure of the clock control circuit.
The 4559 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 4559 Group.
The quartz-crystal oscillator can be used for sub-clock (f(XCIN)).
On-chip oscillator
(internal oscillator)
XIN
XOUT
Ceramic
resonance
RC oscillation
MR1, MR0
11
10
01
Division circuit
Divided by 8
Divided by 4
Divided by 2
MR3, MR2
11
10
01
00
RG0
Multi-
plexer
RG1
System clock (STCK)
Internal clock
generating circuit
(divided by 3)
Instruction clock
(INSTCK)
QS
R
CRCK instruction
Internal reset signal
XCIN
XCOUT
Quartz-crystal
oscillation
Fig 59. Clock control circuit structure
QS
R
QS
R
Key-on wakeup signal
Timer 3 underflow signal
EPOF instruction + POF instruction
EPOF instruction + POF2 instruction
RG2
Rev.1.04 Aug 23, 2007 Page 61 of 146
REJ03B0188-0104