upd78f0730 Renesas Electronics Corporation., upd78f0730 Datasheet - Page 81

• Manufacturer Part Number: upd78f0730
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

5.1 Functions of Clock Generator
The clock generator generates the clock to be supplied to the CPU and peripheral hardware.
The following kinds of system clocks and clock oscillators are selectable.
(1) Main system clock
(2) Internal low-speed oscillation clock (clock for watchdog timer)
Remarks 1. f
<1> X1 oscillator
<2> Internal high-speed oscillator
An external main system clock (f
external main system clock input can be disabled by executing the STOP instruction or using MOC.
As the main system clock, a high-speed system clock (X1 clock or external main system clock) or internal high-
speed oscillation clock can be selected by using the main clock mode register (MCM).
• Internal low-speed oscillator
This circuit oscillates a clock of f
clock always starts operating.
Oscillation can be stopped by using the internal oscillation mode register (RCM) when “internal low-speed
oscillator can be stopped by software” is set by option byte.
The internal low-speed oscillation clock cannot be used as the CPU clock. The following hardware operates
with the internal low-speed oscillation clock.
• Watchdog timer
• 8-bit timer H1 (when f
This circuit oscillates a clock of f
can be stopped by executing the STOP instruction or using the main OSC control register (MOC).
This circuit oscillates a clock of f
operating with this internal high-speed oscillation clock. Oscillation can be stopped by executing the
STOP instruction or using the internal oscillation mode register (RCM).
2. f
3. f
4. f
X
RH
EXCLK
RL
:
:
:
:
X1 clock oscillation frequency
Internal high-speed oscillation clock frequency
External main system clock frequency
Internal low-speed oscillation clock frequency
RL
, f
RL
CHAPTER 5 CLOCK GENERATOR
/2
EXCLK
7
, or f
Preliminary User’s Manual U19014EJ1V0UD
RL
= 240 kHz (TYP.). After a reset release, the internal low-speed oscillation
RL
= 12 or 16 MHz) can also be supplied from the EXCLK/X2/P122 pin. An
X
/2
RH
= 12 or 16 MHz by connecting a resonator to X1 and X2. Oscillation
9
is selected)
= 16 MHz (TYP.). After a reset release, the CPU always starts
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