Datasheet

Section 17 A/D Converter
Rev. 3.00 Sep. 28, 2009 Page 499 of 710
REJ09B0384-0300
17.4.4 Timing of External Trigger Input
A/D conversion can also be started by an externally input trigger signal. Setting the TRGS1 and
TRGS0 bits in ADCSR to B'11 selects the signal on the ADTRG pin as an external trigger. The
ADST bit in ADCSR is set to 1 on the falling edge of ADTRG, initiating A/D conversion. Other
operations are the same as those in the case where the ADST bit is set to 1 by software, regardless
of whether the converter is in single mode or scan mode. The timing of this operation is shown in
figure 17.5.
ADTRG
ADST
A/D conversion time
φ
Internal trigger
signal
Figure 17.5 Timing of External Trigger Input
17.5 Interrupt Source
The A/D converter generates an A/D conversion end interrupt (ADI) at the end of A/D conversion.
Setting the ADIE bit to 1 enables ADI interrupt requests while the ADF bit in ADCSR is set to 1
after A/D conversion ends. The ADI interrupt can be used to activate the DTC. Reading the
converted data by the DTC activated by the ADI interrupt allows consecutive conversion to be
performed without software overhead.
Table 17.5 A/D Converter Interrupt Source
Name Interrupt Source Interrupt Flag DTC Activation
ADI A/D conversion end ADF Possible