RL78/G1H CHAPTER 24 SAFETY FUNCTIONS
R01UH0575EJ0120 Rev. 1.20 Page 791 of 920
Dec 22, 2016
24.3.8 A/D test function
The IEC60730 standard mandates testing the A/D converter. The A/D test function is used to check whether the
A/D converter is operating normally by executing A/D conversions of the positive reference voltage and negative
reference voltage of the A/D converter, analog input channel (ANI). For details on the checking method, refer to
the safety function (A/D test) application note (R01AN0955).
The analog multiplexer can be checked using the following procedure.
(1) Select the ANIx pin as the target for A/D conversion by setting the ADTES register (ADTES1, ADTES0 = 0,
0).
(2) Perform A/D conversion for the ANIx pin (conversion result 1-1).
(3) Select the negative reference voltage of the A/D converter as the target for A/D conversion by setting the
ADTES register (ADTES1, ADTES0 = 1, 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 as the target for A/D conversion by setting the ADTES register (ADTES1, ADTES0 = 0,
0).
(6) Perform A/D conversion for the ANIx pin (conversion result 1-2).
(7) Select the positive reference voltage of the A/D converter as the target for A/D conversion by setting the
ADTES register (ADTES1, ADTES0 = 1, 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 as the target for A/D conversion by setting the ADTES register (ADTES1, ADTES0 = 0,
0).
(10) Perform A/D conversion for the ANIx pin (conversion result 1-3).
(11) Make sure that “conversion result 1-1” = “conversion result 1-2” = “conversion result 1-3”.
(12) Make sure that the A/D conversion results of “conversion result 2-1” are all 0 and those of “conversion result
2-2” are all 1.
Using the procedure above can confirm that the analog multiplexer is selected and all wiring is connected.
Remark 1. If the analog input voltage is variable during conversion in steps (1) to (10) above, use another
method to check the analog multiplexer.
Remark 2. The conversion results might contain an error. Consider an appropriate level of error when comparing
the conversion results.
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