r5f21346mnfp Renesas Electronics Corporation., r5f21346mnfp Datasheet - Page 623

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r5f21346mnfp

Manufacturer Part Number
r5f21346mnfp
Description
Single-chip Mcus Incorporates The R8c Cpu Core
Manufacturer
Renesas Electronics Corporation.
Datasheet

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Part Number:
r5f21346mnfp#V0
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R8C/34M Group
R01UH0131EJ0100 Rev.1.00
Jun 21, 2011
28.3.4
28.3.5
28.3.6
28.3.7
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. The contents of the ADi register are undefined after a reset. Values
cannot be written to the ADi register.
In repeat mode 0, no interrupt request is generated. After the first AD 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 to 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 and no interrupt is generated. The value of the ADi register before A/D conversion may also be
undefined.
If the ADST bit is set to 0 by a program, do not use the value of all the ADi 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 1 φ AD cycle or more
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
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 OCVREFAN bit in the OCVREFCR register to select the on-chip reference voltage.
The A/D conversion result of the on-chip reference voltage in one-shot mode or in repeat mode 0 is stored in the
AD0 register.
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 28.5 shows the A/D Open-Circuit Detection Example on AVCC Side (Precharge before Conversion
Selected) and Figure 28.6 shows the A/D Open-Circuit Detection Example on AVSS Side (Discharge before
Conversion Selected).
A/D Conversion Result
Low Current Consumption Function
On-Chip Reference Voltage (OCVREF)
A/D Open-Circuit Detection Assist Function
28. A/D Converter
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