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RL78/G1A CHAPTER 22 SAFETY FUNCTIONS
22.3.8 A/D test function
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The IEC60730 standard mandates testing the A/D converter. The A/D test function checks whether or not the A/D
converter is operating normally by executing A/D conversions of the A/D converter’s positive and negative reference
voltages, analog input channel (ANI), temperature sensor output voltage, and the internal reference voltage. For details of
the check method, see the safety function (A/D test) application note (R01AN0955).
The analog multiplexer can be checked using the following procedure.
<1> Select the ANIx pin for A/D conversion using the ADTES register (ADTES1 = 0, ADTES0 = 0).
<2> Perform A/D conversion for the ANIx pin (conversion result 1-1).
<3> Select the A/D converter’s negative reference voltage for A/D conversion using the ADTES register (ADTES1 = 1,
ADTES0 = 0)
<4> Perform A/D conversion of the negative reference voltage of the A/D converter (conversion result 2-1).
<5> Select the ANIx pin for A/D conversion using the ADTES register (ADTES1 = 0, ADTES0 = 0).
<6> Perform A/D conversion for the ANIx pin (conversion result 1-2).
<7> Select the A/D converter’s positive reference voltage for A/D conversion using the ADTES register (ADTES1 = 1,
ADTES0 = 1)
<8> Perform A/D conversion of the positive reference voltage of the A/D converter (conversion result 2-2).
<9> Select the ANIx pin for A/D conversion using the ADTES register (ADTES1 = 0, ADTES0 = 0).
<10> Perform A/D conversion for the ANIx pin (conversion result 1-3).
<11> Check that the conversion results 1-1, 1-2, and 1-3 are equal.
<12> Check that the A/D conversion result 2-1 is all zero and conversion result 2-2 is all one.
Using the procedure above can confirm that the analog multiplexer is selected and all wiring is connected.
Remarks 1. If the analog input voltage is variable during A/D conversion in steps <1> to <10> above, use another
method to check the analog multiplexer.
2. The conversion results might contain an error. Consider an appropriate level of error when comparing
the conversion results.
R01UH0305EJ0200 Rev.2.00 786
Jul 04, 2013