Interrupt Sources And Dtc Transfer Requests; Interrupt Requests; Allowable Impedance Of Signal Source - Renesas RX100 Series User Manual

RX13T Group
26.4

Interrupt Sources and DTC Transfer Requests

26.4.1

Interrupt Requests

The 12-bit A/D converter can send scan end interrupt requests S12ADI, GBADI, and GCADI to the CPU.
Setting the ADCSR.ADIE bit to 1 and 0 enables and disables an S12ADI interrupt, respectively; similarly, setting the
ADCSR.GBADIE bit to 1 and 0 enables and disables a GBADI interrupt, respectively; similarly, setting the
ADGCTRGR.GCADIE bit to 1 and 0 enables and disables a GCADI interrupt, respectively.
In addition, the DTC can be activated when an S12ADI, a GBADI, or GCADI interrupt is generated. Using an S12ADI,
a GBADI, or GCADI interrupt to allow the DTC to read the converted data enables sequence conversion without burden
on software.
For details on DTC settings, see section 16, Data Transfer Controller (DTCb) .
26.5

Allowable Impedance of Signal Source

To achieve high-speed conversion of 1.4 μs, the analog input pins of this MCU are designed so that the conversion
accuracy is guaranteed if the impedance of the input signal source is 1.0 kΩ or less. If an external capacitor of large
capacitance is attached in the application in which only a single pin input is converted in single scan mode, the only load
on input is virtually 2.5 kΩ of the internal input resistor; therefore, the impedance of the signal source can be ignored.
Being a low-pass filter, however, an analog input circuit may not follow the analog signal with a large differential
coefficient. When high-speed analog signals are to be converted or multiple pins are to be converted in scan mode, a low-
impedance buffer should be used.
Figure 26.32 shows an equivalent circuit of an analog input pin and an external sensor.
To perform A/D conversion accurately, charging of the internal capacitor C shown in Figure 26.32 must be completed
within the specified period of time. This specified period is referred to as sampling time.
Sensor equivalent circuit
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Figure 26.32 Equivalent Circuit of Analog Input Pin and External Sensor
R01UH0822EJ0100 Rev.1.00
Jul 31, 2019
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C
VC
26. 12-Bit A/D Converter (S12ADF)
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