519
14.5
Interrupts
The A/D converter generates an A/D conversion end interrupt (ADI) at the end of A/D conversion.
ADI interrupt requests can be enabled or disabled by means of the ADIE bit in ADCSR.
The DTC can be activated by an ADI interrupt. Having the converted data read by the DTC in
response to an ADI interrupt enables continuous conversion to be achieved without imposing a
load on software.
The A/D converter interrupt source is shown in table 14.5.
Table 14.5
A/D Converter Interrupt Source
Interrupt Source
Description
DTC Activation
ADI
Interrupt due to end of conversion
Possible
14.6
Usage Notes
The following points should be noted when using the A/D converter.
Setting Range of Analog Power Supply and Other Pins:
(1) Analog input voltage range
The voltage applied to analog input pins AN0 to AN7 during A/D conversion should be in the
range AV
SS
≤
ANn
≤
V
ref
.
(2) Relation between AV
CC
, AV
SS
and V
CC
, V
SS
As the relationship between AV
CC
, AV
SS
and V
CC
, V
SS
, set, AV
CC
= V
CC
and AV
SS
= V
SS
. If the
A/D converter is not used, the AV
CC
and AV
SS
pins must on no account be left open.
(3) V
ref
input range
The analog reference voltage input at the V
ref
pin set in the range V
ref
≤
AV
CC
.
If conditions (1), (2), and (3) above are not met, the reliability of the device may be adversely
affected.
Notes on Board Design:
In board design, digital circuitry and analog circuitry should be as
mutually isolated as possible, and layout in which digital circuit signal lines and analog circuit
signal lines cross or are in close proximity should be avoided as far as possible. Failure to do so
may result in incorrect operation of the analog circuitry due to inductance, adversely affecting A/D
conversion values.