UPD78F9234MC-5A4-A Datasheet, PDF (400/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

APPENDIX D LIST OF CAUTIONS
Function
Details of
Function
Cautions
(9/20)
Page
A/D
converter
PMC2: Port
mode control
register 2
When PMC20 to PMC23 are set to 1, the P20/ANI0 to P23/ANI3 pins cannot p.171
be used as port pins. Be sure to set the pull-up resistor option registers (PU20
to PU23) to 0 for the pins set to A/D converter mode.
A/D converter
operations
Make sure the period of <1> to <4> is 1 μs or more.
pp.
172, 176
It is no problem if the order of <1> and <2> is reversed.
pp.
172, 176
<1> can be omitted. However, ignore the data resulting from the first
conversion after <4> in this case.
p.176
The period from <5> to <8> differs from the conversion time set using bits 5 to p.176
3 (FR2 to FR0) of ADM. The period from <7> to <8> is the conversion time
set using FR2 to FR0.
Operating current To satisfy the DC characteristics of the supply current in the STOP mode,
p.179
in STOP mode clear bit 7 (ADCS) and bit 0 (ADCE) of the A/D converter mode register (ADM)
to 0 before executing the STOP instruction.
Input range of
ANI0 to ANI3
Observe the rated range of the ANI0 to ANI3 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.179
Conflicting
operations
ADCR, ADCRH read has priority. After the read operation, the new
conversion result is written to ADCR, ADCRH.
p.179
ADM or ADS write has priority. ADCR, ADCRH write is not performed, nor is p.179
the conversion end interrupt signal (INTAD) generated.
Noise
To maintain the 10-bit resolution, attention must be paid to noise input to the
countermeasures AVREF pin and pins ANI0 to ANI3.
p.179
<1> Connect a capacitor with a low equivalent resistance and a high
frequency response to the power supply.
<2> Because the effect increases in proportion to the output impedance of the
analog input source, it is recommended that a capacitor be connected
externally, as shown in Figure 10-19, to reduce noise.
<3> Do not switch the A/D conversion function of the ANI0 to ANI3 pins to
their alternate functions during conversion.
<4> The conversion accuracy can be improved by setting HALT mode
immediately after the conversion starts.
ANI0/P20 to
ANI3/P23
The analog input pins (ANI0 to ANI3) are also used as input port pins (P20 to
P23).
When A/D conversion is performed with any of ANI0 to ANI3 selected, do not
access port 2 (P20 to P23) while conversion is in progress; otherwise the
conversion resolution may be degraded.
p.180
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.180
398
User’s Manual U17446EJ5V0UD