UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 195

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

Cautions 1. A voltage oscillation stabilization time of 1.93 to 5.39 ms is required after the supply voltage
Remark The clock which is not used as a CPU clock can be suspended by setup of software during
<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 canceled and the oscillation start of the high-
<3> After reset release, after reset processing is performed, CPU carries out a start of operation with high-speed
<4> X1 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
speed oscillator will be carried out automatically.
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).
microcomputer operation. Moreover, high-speed oscillation clock and a high-speed system clock can
suspend a clock by execution of a STOP command (see (4) in 5.6.1 Controlling high-speed system
clock, (3) in 5.6.2 Example of controlling internal high-speed oscillation clock, and (4) in 5.6.3
Example of controlling subsystem clock).
2. It is not necessary to wait for the oscillation stabilization time when an external clock input
reaches 1.59 V (TYP.). If the supply voltage rises from 1.59 V (TYP.) to 2.7 V (TYP.) within
1.93 ms, the power supply oscillation stabilization time of 0 to 5.39 ms is automatically
generated before reset processing.
from the EXCLK and EXCLKS pins is used.
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
193