HD64F38602R Datasheet, PDF (108/552 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

Section 4 Clock Pulse Generators
4.5.4 Note on Subclock Stop State
To stop the subclock, a state transition should not be made except to mode in which the system
clock operates. If the state transition is made to other mode, it may result in incorrect operation.
4.5.5 Note on the Oscillation Stabilization of Resonators
When a microcomputer operates, the internal power supply potential fluctuates slightly in
synchronization with the system clock. Depending on the individual resonator characteristics, the
oscillation waveform amplitude may not be sufficiently large immediately after the oscillation
stabilization wait time, making the oscillation waveform susceptible to influence by fluctuations in
the power supply potential. In this state, the oscillation waveform may be disrupted, leading to an
unstable system clock and incorrect operation of the microcomputer.
If incorrect operation occurs, change the setting of the standby timer select bits 2 to 0 (STS2 to
STS0) (bits 6 to 4 in the system control register 1 (SYSCR1)) to give a longer wait time.
For example, if incorrect operation occurs with a wait time setting of 512 states, check the
operation with a wait time setting of 1,024 states or more.
If the same kind of incorrect operation occurs after a reset as after a state transition, hold the RES
pin low for a longer period.
4.5.6 Note on Using Power-On Reset
The power-on reset circuit in this LSI adjusts the reset clear time by the capacitor capacitance,
which is externally connected to the RES pin. The external capacitor capacitance should be
adjusted to secure the oscillation stabilization time before reset clearing. For details, refer to
section 19, Power-On Reset Circuit.
4.5.7 Note on Using On-Chip Emulator
When the on-chip emulator is used, system clock accuracy is necessary for flash memory
programming/erasing. The frequency of the on-chip oscillator differs depending on the voltage
and temperature conditions. Therefore, when using the on-chip emulator, the resonator must be
connected to the OSC1 and OSC2 pins or an external clock must be supplied. In this case, the on-
chip oscillator is used for user program execution, and the system clock is used for flash memory
programming/erasing. This control is handled when the E7_2 pin is fixed to high level during a
reset by the on-chip emulator.
Rev. 3.00 May 15, 2007 Page 76 of 516
REJ09B0152-0300