APPENDIX D LIST OF CAUTIONS
User’s Manual U16899EJ2V0UD
538
(24/24)
Chapter
Cl
assi
fi
cati
on
Function Details
of
Function
Cautions Page
Absolute
maximum
ratings
Product quality may suffer if the absolute maximum rating is exceeded even
momentarily for any parameter. That is, the absolute maximum ratings are rated
values at which the product is on the verge of suffering physical damage, and
therefore the product must be used under conditions that ensure that the absolute
maximum ratings are not exceeded.
p. 473
When using the high-speed system clock oscillator, wire as follows in the area
enclosed by the broken lines in the above figures to avoid an adverse effect from
wiring capacitance.
•
Keep the wiring length as short as possible.
•
Do not cross the wiring with the other signal lines.
•
Do not route the wiring near a signal line through which a high fluctuating
current
flows.
•
Always make the ground point of the oscillator capacitor the same potential as
V
SS
.
•
Do not ground the capacitor to a ground pattern through which a high current
flows.
•
Do not fetch signals from the oscillator.
p. 474
High-speed
system clock
(crystal/
ceramic)
oscillator
Since the CPU is started by the Ring-OSC after reset, check the oscillation
stabilization time of the high-speed system clock using the oscillation stabilization
time status register (OSTC). Determine the oscillation stabilization time of the
OSTC register and oscillation stabilization time select register (OSTS) after
sufficiently evaluating the oscillation stabilization time with the resonator to be
used.
p. 474
Recommended
oscillator
constants
The oscillator constants shown above are reference values based on evaluation
in a specific environment by the resonator manufacturer. If it is necessary to
optimize the oscillator characteristics in the actual application, apply to the
resonator manufacturer for evaluation on the implementation circuit. The
oscillation voltage and oscillation frequency only indicate the oscillator
characteristic. Use the 78K0/KE1+ so that the internal operation conditions are
within the specifications of the DC and AC characteristics.
p. 475
When using the subsystem clock oscillator, wire as follows in the area enclosed
by the broken lines in the above figure to avoid an adverse effect from wiring
capacitance.
•
Keep the wiring length as short as possible.
•
Do not cross the wiring with the other signal lines.
•
Do not route the wiring near a signal line through which a high fluctuating
current
flows.
•
Always make the ground point of the oscillator capacitor the same potential as
V
SS
.
•
Do not ground the capacitor to a ground pattern through which a high current
flows.
•
Do not fetch signals from the oscillator.
p. 476
Chapter 29
Hard
Electrical
specifications
Subsystem
clock
oscillator
The subsystem clock oscillator is designed as a low-amplitude circuit for reducing
power consumption, and is more prone to malfunction due to noise than the high-
speed system clock oscillator. Particular care is therefore required with the wiring
method when the subsystem clock is used.
p. 476
Chapter 32
Soft
Wait
−
When the CPU is operating on the subsystem clock and the high-speed system
clock is stopped (MCC = 1), do not access the registers listed above using an
access method in which a wait request is issued.
p. 496
