4509 Datasheet, PDF (56/142 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4509 Group
CLOCK CONTROL
The clock control circuit consists of the following circuits.
• On-chip oscillator (internal oscillator)
• Ceramic oscillation circuit
• RC 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 49 shows the structure of the clock control circuit.
The 4509 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
source oscillation (f(XIN)) of the 4509 Group.
On-chip oscillator
f(RING)
MR0
1
f(XIN)
0
XIN
XOUT
Ceramic resonator
circuit
Multiplexer
RC oscillation circuit
Division circuit
divided by 8
divided by 4
divided by 2
MR3, MR2
11
10
01
00
System clock
Internal clock
generation circuit
(divided by 3)
Instruction clock
(INSTCK)
RG0
QS
CRCK instruction
QR
Internal reset signal
MR1
QS
R
Key-on wakeup signal
EPOF instruction + POF instruction
Fig. 49 Clock control circuit structure
Rev.1.02 2006.12.22 page 56 of 140
REJ03B0147-0102