R01UH0822EJ0100 Rev.1.00
Page 878 of 1041
Jul 31, 2019
RX13T Group
26. 12-Bit A/D Converter (S12ADF)
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.
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
must be completed
within the specified period of time. This specified period is referred to as sampling time.
Figure 26.32
Equivalent Circuit of Analog Input Pin and External Sensor
VC
VIN
t
VIN
R0
Sensor equivalent circuit
C
R