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APPENDIX B LIST OF CAUTIONS
User’s Manual U17854EJ9V0UD
830
(6/33)
Chapter
Cl
assi
fi
cati
on
Function
Details of
Function
Cautions
Page
Soft
Clock
generator
HIOTRM:
Internal-high-
speed
oscillator
trimming register
The
internal
high-speed
oscillation
frequency
becomes
faster/slower
by
increasing/decreasing the HIOTRM value to a value larger/smaller than a certain
value.
A
reversal,
such
as
the
frequency
becoming
slower/faster
by
increasing/decreasing the HIOTRM value does not occur.
p.155
When using the X1 oscillator and XT1 oscillator, wire as follows in the area enclosed
by the broken lines in the Figures 5-10 and 5-11 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 VSS.
Do not ground the capacitor to a ground pattern through which a high current flows.
Do not fetch signals from the oscillator.
Note that the XT1 oscillator is designed as a low-amplitude circuit for reducing power
consumption.
p.157
X1/XT1
oscillator
When X2 and XT1 are wired in parallel, the crosstalk noise of X2 may increase with
XT1, resulting in malfunctioning.
p.158
If the voltage rises with a slope of less than 0.5 V/ms (MIN.) from power application
until the voltage reaches 1.8 V, input a low level to the RESET pin from power
application until the voltage reaches 1.8 V, or set the LVI default start function
stopped by using the option byte (LVIOFF = 0) (see Figure 5-14). By doing so, the
CPU operates with the same timing as <2> and thereafter in Figure 5-13 after reset
release by the RESET pin.
p.162
When LVI
default start
function stopped
is set (option
byte: LVIOFF =
1)
It is not necessary to wait for the oscillation stabilization time when an external clock
input from the EXCLK pin is used.
p.162
A voltage oscillation stabilization time is required after the supply voltage reaches
1.59 V (TYP.). If the supply voltage rises from 1.59 V (TYP.) to 2.07 V (TYP.) within
the power supply oscillation stabilization time, the power supply oscillation
stabilization time is automatically generated before reset processing.
p.163
Hard
Clock
generator
operation
when
power
supply
voltage is
turned on
When LVI
default start
function enabled
is set (option
byte: LVIOFF =
0)
It is not necessary to wait for the oscillation stabilization time when an external clock
input from the EXCLK pin is used.
p.163
X1/P121,
X2/EXCLK/P122
The X1/P121 and X2/EXCLK/P122 pins are in the input port mode after a reset
release.
p.164
The CMC register can be written only once after reset release, by an 8-bit memory
manipulation instruction.
Therefore, it is necessary to also set the value of the
OSCSELS bit at the same time. For OSCSELS bit, see 5.6.3 Example of controlling
subsystem clock.
p.164
X1 clock
Set the X1 clock after the supply voltage has reached the operable voltage of the
clock to be used (see CHAPTER 27 ELECTRICAL SPECIFICATIONS (STANDARD
PRODUCTS) and CHAPTER 28 ELECTRICAL SPECIFICATIONS ((A) GRADE
PRODUCTS)).
p.164
Chapter
5
Soft
Controlling
high-speed
system
clock
External main
system clock
The CMC register can be written only once after reset release, by an 8-bit memory
manipulation instruction.
Therefore, it is necessary to also set the value of the
OSCSELS bits at the same time.
For OSCSELS bits, see 5.6.3 Example of
controlling subsystem clock.
p.165