r5f21368sdfp Renesas Electronics Corporation., r5f21368sdfp Datasheet - Page 578

• Manufacturer Part Number: r5f21368sdfp
• Description: Renesas Mcu R8c Family / R8c/3xt-a Series
• Manufacturer: Renesas Electronics Corporation.

Under development
R8C/36T-A Group
R01UH0240EJ0001 Rev.0.01
Apr 28, 2011
23.3.4
23.3.5
23.3.6
23.3.7
23.3.8
The A/D conversion result is stored in the ADi register (i = 0 to 7). The register where the result is stored varies
depending on the A/D operating mode used. Values cannot be written to the ADi register.
In repeat mode 0, no interrupt request is generated. After the first A/D conversion is completed, determine if the
A/D conversion time has elapsed by a program.
In one-shot mode, repeat mode 1, single sweep mode, and repeat sweep mode, an interrupt request is generated
at certain times, such as when an A/D conversion completes (the IR bit in the ADIC register is set to 1).
However, in repeat mode 1 and repeat sweep mode, A/D conversion continues after an interrupt request is
generated. Read the ADi register before the next A/D conversion is completed, since at completion the ADi
register is rewritten with the new value.
In one-shot mode and single sweep mode, when bits ADCAP1 and ADCAP0 in the ADMOD register is set to
00b (software trigger), the ADST bit in the ADCON0 register is used to determine whether the A/D conversion
or sweep has completed.
During an A/D conversion operation, if the ADST bit in the ADCON0 register is set to 0 (A/D conversion
stops) by a program to forcibly terminate A/D conversion, the conversion result of the A/D converter is
undefined. An A/D conversion interrupt request may be generated depending the timing when the ADST bit is
written. When the ADST bit is set to 0 by a program, do not use the value of the ADi register and an A/D
conversion interrupt.
During an A/D conversion operation, after the ADST bit in the ADCON0 register is set to 0 (A/D conversion
stops) by a program to forcibly end the conversion, allow at least two cycles of the  AD clock before writing 1
to the ADST bit to ensure time for end processing.
Either 8 bits or 10 bits can be selected as the resolution of the A/D converter. 8-bit/10 bit mode can be selected
by the BITS bit in the ADCON1 register.
When the A/D converter is not used, power consumption can be reduced by setting the ADSTBY bit in the
ADCON1 register to 0 (A/D operation stops (standby)) to shut off any analog circuit current flow.
To use the A/D converter, set the ADSTBY bit to 1 (A/D operation enabled) and wait for at least one  AD cycle
before setting the ADST bit in the ADCON0 register to 1 (A/D conversion starts). Do not write 1 to bits ADST
and ADSTBY at the same time.
Also, do not set the ADSTBY bit to 0 (A/D operation stops (standby)) during A/D conversion.
In one-shot mode, repeat mode 0, and repeat mode 1, the on-chip reference voltage (OCVREF) can be used as
an analog input.
Any variation in VREF can be confirmed using the on-chip reference voltage.
Use the ADEX0 bit in the ADCON1 register and the VREFMON bit in the OCVREFCR register to select the
on-chip reference voltage.
When setting the ADEX0 bit to 1, select bits CH2 to CH0 in the ADINSEL register to be 000b. The A/D
conversion result of the on-chip reference voltage in repeat mode 1 is stored in one of registers AD0 to AD7,
depending on the number of conversions.
To suppress influences of the analog input voltage leakage from the previously converted channel during A/D
conversion operation, a function is incorporated to fix the electric charge on the chopper amp capacitor to the
predetermined state (AVCC or GND) before starting conversion.
This function enables more reliable detection of an open circuit in the wiring connected to the analog input pins.
Figure 23.6 shows the A/D Open-Circuit Detection Example on AVCC Side (Precharge before Conversion
Selected) (i = 0 to 11) and Figure 23.7 shows the A/D Open-Circuit Detection Example on AVSS Side
(Discharge before Conversion Selected) (i = 0 to 11).
A/D Conversion Result
Resolution (8-Bit/10-Bit Mode)
Low-Current-Consumption Function
On-Chip Reference Voltage (OCVREF)
A/D Open-Circuit Detection Assist Function
Preliminary document
Specifications in this document are tentative and subject to change.
23. A/D Converter
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