UPD78F0537DGA(T)-9EV-A NEC, UPD78F0537DGA(T)-9EV-A Datasheet - Page 738

• Manufacturer Part Number: UPD78F0537DGA(T)-9EV-A
• Description: 8BIT MCU, 128K FLASH, 7KB RAM, SMD
• Manufacturer: NEC

Specifications of UPD78F0537DGA(T)-9EV-A

• Controller Family/series: UPD78
• No. Of I/o's: 55
• Ram Memory Size: 7KB
• Cpu Speed: 20MHz
• No. Of Timers: 8
• No. Of Pwm: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 128KB
• Oscillator Type: External, Internal

738
A/D
converter
Function
Input range of
ANI0 to ANI7
Conflicting
operations
Noise
countermeasures
ANI0/P20 to
ANI7/P27
Input impedance
of ANI0 to ANI7
pins
AV
impedance
Interrupt request
flag (ADIF)
REF
Details of
Function
pin input
Observe the rated range of the ANI0 to ANI7 input voltage. If a voltage of AV
or higher and AV
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.
If conflict occurs 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.
If conflict occurs 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.
To maintain the 10-bit resolution, attention must be paid to noise input to the
AV
• Connect a capacitor with a low equivalent resistance and a good frequency
• The higher the output impedance of the analog input source, the greater the
• Do not switch these pins with other pins during conversion.
• The accuracy is improved if the HALT mode is set immediately after the start of
The analog input pins (ANI0 to ANI7) are also used as I/O 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 AV
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.
This A/D converter charges a sampling capacitor for sampling during sampling
time.
Therefore, only a leakage current flows when sampling is not in progress, and a
current that charges the capacitor flows during sampling. Consequently, the input
impedance fluctuates depending on whether sampling is in progress, and on the
other states.
To make sure that sampling is effective, however, it is recommended to keep the
output impedance of the analog input source to within 10 kΩ, and to connect a
capacitor of about 100 pF to the ANI0 to ANI7 pins (see Figure 13-20).
A series resistor string of several tens of kΩ is connected between the AV
AV
Therefore, if the output impedance of the reference voltage source is high, this will
result in a series connection to the series resistor string between the AV
AV
The interrupt request flag (ADIF) is not cleared even if the analog input channel
specification register (ADS) is changed. Therefore, if an analog input pin is
changed during A/D conversion, the A/D conversion result and ADIF for the pre-
change analog input may be set just before the ADS rewrite. Caution is therefore
required since, at this time, when ADIF is read immediately after the ADS rewrite,
ADIF is set despite the fact A/D conversion for the post-change analog input has
not ended. When A/D conversion is stopped and then resumed, clear ADIF
before the A/D conversion operation is resumed.
response to the power supply.
influence. To reduce the noise, connecting external C as shown in Figure 13-
20 is recommended.
conversion.
REF
SS
SS
pins.
pins, resulting in a large reference voltage error.
pin and pins ANI0 to ANI7.
APPENDIX D LIST OF CAUTIONS
User’s Manual U17260EJ6V0UD
SS
or lower (even in the range of absolute maximum ratings) is
Cautions
REF
.
REF
REF
and
and
REF
p. 330
p. 330
p. 330
p. 330
p. 331
p. 331
p. 331
p. 331
p. 332
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