UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 205

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

5.6.4 Controlling internal low-speed oscillation clock
driven (240 kHz (TYP.)) if the watchdog timer operation has been enabled by the option byte.
5.6.5 Clocks supplied to CPU and peripheral hardware
of registers.
The internal low-speed oscillation clock is a clock for the watchdog timer. It cannot be used as the CPU clock.
With this clock, only the following peripheral hardware can operate.
In addition, the following operation modes can be selected by the option byte.
The internal low-speed oscillator automatically starts oscillation after a reset release, and the watchdog timer is
(1) To stop the internal low-speed oscillation clock (example of setting method)
(2) To oscillate the internal low-speed oscillation clock (example of setting method)
The following table shows the relation among the clocks supplied to the CPU and peripheral hardware, and setting
Remarks 1. XSEL:
Watchdog timer
8-bit timer H1 (if f
Internal low-speed oscillation clock oscillation cannot be stopped
Internal low-speed oscillation clock oscillation can be stopped by software
Caution If “Internal low-speed oscillation clock oscillation cannot be stopped” is selected by the option
<1> Setting LSRSTOP to 1 (RCM register)
<1> Clearing LSRSTOP to 0 (RCM register)
XSEL
0
0
1
1
1
1
1
1
1
1
If LSRSTOP is set to 1, the internal low-speed oscillator oscillation is stopped.
If LSRSTOP is cleared to 0, the internal low-speed oscillation clock is oscillated.
2. CSS:
3. MCM0: Bit 0 of MCM
4. EXCLK: Bit 7 of the clock operation mode select register (OSCCTL)
Table 5-3. Clocks Supplied to CPU and Peripheral Hardware, and Register Setting
byte, oscillation of the internal low-speed oscillation clock cannot be controlled.
CSS
0
1
0
0
0
0
1
1
1
1
OSC
is selected as the count clock)
Bit 2 of the main clock mode register (MCM)
Bit 4 of the processor clock control register (PCC)
MCM0
×
×
0
0
1
1
0
0
1
1
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
EXCLK
×
×
0
1
0
1
0
1
0
1
Internal high-speed oscillation clock
Subsystem clock
Internal high-speed oscillation
clock
X1 clock
External main system clock
Subsystem clock
Clock Supplied to CPU
Supplied Clock
Internal high-speed oscillation
clock
X1 clock
External main system clock
X1 clock
External main system clock
X1 clock
External main system clock
Clock Supplied to Peripheral
Hardware
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