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APPENDIX B LIST OF CAUTIONS
User’s Manual U17854EJ9V0UD
838
(14/33)
Chapter
Cl
assi
fi
cati
on
Function
Details of
Function
Cautions
Page
Procedure for
Using
Temperature
Sensors.
Use the result of the second or later A/D conversion for temperature sensor 0 (ANI0
side), and the result of the third or later A/D conversion for temperature sensor 1
(ANI1 side).
p. 325
Operating
current in STOP
mode
Shift to STOP mode after clearing the A/D converter (by clearing bit 7 (ADCS) of the
A/D converter mode register (ADM) to 0). The operating current can be reduced by
clearing bit 0 (ADCE) of the A/D converter mode register (ADM) to 0 at the same time.
To restart from the standby status, clear bit 0 (ADIF) of interrupt request flag register
1L (IF1L) to 0 and start operation.
p.328
Soft
Reducing
current when
A/D converter is
stopped
Be sure that the voltage to be applied to AVREF normally satisfies the conditions
stated in Table 10-1.
If bit 7 (ADCS) and bit 0 (ADCE) of the A/D converter mode register (ADM) are set to
0, the current will not be increased by the A/D converter even if a voltage is applied
to AVREF, while the A/D converter is stopped. If a current flows from the power supply
that supplies a voltage to AVREF to an external circuit of the microcontroller as shown
in Figure 10-25, AVREF = 0 V = AVSS can be achieved and the external current can be
reduced by satisfying the following conditions (see the main text).
p.328
Hard
Input range of
ANI0 to ANI7
Observe the rated range of the ANI0 to ANI7 input voltage. If a voltage of AVREF or
higher and AVSS or lower (even in the range of absolute maximum ratings) is input to
an analog input channel, the converted value of that channel becomes undefined. In
addition, the converted values of the other channels may also be affected.
p.329
Conflict between A/D conversion result register (ADCR, ADCRH) write and ADCR or
ADCRH read by instruction upon the end of conversion
ADCR or ADCRH read has priority. After the read operation, the new conversion
result is written to ADCR or ADCRH.
p.329
Soft
Conflicting
operations
Conflict between ADCR or ADCRH write and A/D converter mode register (ADM)
write, analog input channel specification register (ADS), or A/D port configuration
register (ADPC) write upon the end of conversion
ADM, ADS, or ADPC write has priority. ADCR or ADCRH write is not performed, nor
is the conversion end interrupt signal (INTAD) generated.
p.329
Hard
Noise
countermeasures
To maintain the 10-bit resolution, attention must be paid to noise input to the AVREF
pin and pins ANI0 to ANI7.
<1> Connect a capacitor with a low equivalent resistance and a good frequency
response to the power supply.
<2> The higher the output impedance of the analog input source, the greater the
influence. To reduce the noise, connecting external C as shown in Figure 10-26
is recommended.
<3> Do not switch these pins with other pins during conversion.
<4> The accuracy is improved if the HALT mode is set immediately after the start of
conversion.
p.329
Soft
The analog input pins (ANI0 to ANI7) are also used as input port pins (P20 to P27).
When A/D conversion is performed with any of ANI0 to ANI7 selected, do not access
P20 to P27 while conversion is in progress; otherwise the conversion resolution may
be degraded. It is recommended to select pins used as P20 to P27 starting with the
ANI0/P20 that is the furthest from AVREF
p.330
Chapter
1
0
Hard
A/D
converter
ANI0/P20 to
ANI7/P27
If a digital pulse is applied to the pins adjacent to the pins currently used for A/D
conversion, the expected value of the A/D conversion may not be obtained due to
coupling noise.
Therefore, do not apply a pulse to the pins adjacent to the pin
undergoing A/D conversion.
p.330