4571 Datasheet, PDF (49/126 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4571 Group
CLOCK CONTROL
The clock control circuit consists of the following circuits.
• Ceramic oscillation 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 50 shows the structure of the clock control circuit.
XIN
Ceramic
oscillation circuit
Division circuit
divided by 8
divided by 4
divided by 2
MR3, MR2
11
10
01
00
System clock
(STCK)
Internal clock
generation circuit
(divided by 3)
Instruction clock
(INSTCK)
Oscillation
stop signal
Voltage drop detection circuit
(reset occurs)
QS
R
EPOF instruction + POF instruction
Key-on wakeup signal
RESET
Fig 50. Clock control circuit structure
Rev.1.02 May 25, 2007 Page 49 of 124
REJ03B0179-0102