Datasheet

RL78/L12 CHAPTER 23 SAFETY FUNCTIONS
R01UH0330EJ0200 Rev.2.00 791
Dec 13, 2013
23.3.8 A/D test function
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.
<R>