Renesas rl78 User Manual

 

RL78/G1A 

CHAPTER  22   SAFETY  FUNCTIONS 

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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 

 

 

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Jul 04, 2013