UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 193

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

(2) Improvement of performance
Subsystem clock (f
oscillation clock (f
(when XT1 oscillation
(when X1 oscillation
Internal high-speed
Internal reset signal
Notes 1.
system clock (f
Because the CPU can be started without waiting for the X1 clock oscillation stabilization time, the total
performance can be improved.
A timing diagram of the CPU default start using the internal high-speed oscillation clock is shown in Figures 5-12
and 5-13.
<1> The internal reset signal by the power-on clear (POC) circuit is generated after a power supply injection.
<2> If power supply voltage exceeds 1.59 V (TYP.), reset will be released and the oscillation start of the high-
<3> If power supply voltage is rose by inclination of 0.5 V/ms (MIN.), after the voltage stable waiting time of a
<4> One clock or XT1 clock should set up an oscillation start by software (see (1) in 5.6.1 Controlling high-
<5> When you change CPU to X1 clock or XT1 clock, set up a change by software after the oscillation stability
Power supply
voltage (V
High-speed
CPU clock
speed oscillator will be carried out automatically.
power supply/regulator passed after reset release and reset processing will be performed, CPU carries out a
start of operation with high-speed oscillation clock.
speed system clock and (1) in 5.6.3 Example of controlling subsystem clock).
waiting of a clock (see (3) in 5.6.1 Controlling high-speed system clock and (3) in 5.6.3 Example of
controlling subsystem clock).
Figure 5-12 Operation of the Clock Generating Circuit When Power Supply Voltage Injection
selected)
selected)
2.
OSC8
DD
SUB
0 V
IN
The internal voltage stabilization time includes the oscillation accuracy stabilization time of the internal
high-speed oscillation clock.
When releasing a reset (above figure) or releasing STOP mode while the CPU is operating on the
internal high-speed oscillation clock, confirm the oscillation stabilization time for the X1 clock using the
oscillation stabilization time counter status register (OSTC). If the CPU operates on the high-speed
system clock (X1 oscillation), set the oscillation stabilization time when releasing STOP mode using the
oscillation stabilization time select register (OSTS).
)
)
)
)
<1>
1.59 V
(TYP.)
(When 1.59 V POC mode setup (option byte: LVISTART = 0))
<3> Waiting for
voltage stabilization
<2>
0.5 V/ms
(1.93 to 5.39 ms)
(MIN.)
Note 1
1.8 V
Starting X1 oscillation
is set by software.
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
Starting XT1 oscillation
is set by software.
Internal high-speed oscillation clock
Reset processing
<4>
(11 to 45 s)
oscillation stabilization time:
<4>
2
11
/f
X
X1 clock
to 2
16
/f
X
Note 2
<5>
High-speed system clock
Switched by
software
<5>
Subsystem clock
191