319
12.3.3
A/D Converter Operation Modes
A/D converter operation modes are shown in table 12.3.
Table 12.3
A/D Converter Operation Modes
Operation
Mode
Reset
Active
Sleep
Watch
Subactive Subsleep Standby
Module
Standby
AMR
Reset
Functions Functions Held
Held
Held
Held
Held
ADSR
Reset
Functions Functions Held
Held
Held
Held
Held
ADRRH
Held
*
Functions Functions Held
Held
Held
Held
Held
ADRRL
Held
*
Functions Functions Held
Held
Held
Held
Held
Note:
*
Undefined in a power-on reset.
12.4
Interrupts
When A/D conversion ends (ADSF changes from 1 to 0), bit IRRAD in interrupt request register 2
(IRR2) is set to 1.
A/D conversion end interrupts can be enabled or disabled by means of bit IENAD in interrupt
enable register 2 (IENR2).
For further details see 3.3, Interrupts.
12.5
Typical Use
An example of how the A/D converter can be used is given below, using channel 1 (pin AN1) as
the analog input channel. Figure 12.3 shows the operation timing.
1. Bits CH3 to CH0 of the A/D mode register (AMR) are set to 0101, making pin AN
1
the analog
input channel. A/D interrupts are enabled by setting bit IENAD to 1, and A/D conversion is
started by setting bit ADSF to 1.
2. When A/D conversion is complete, bit IRRAD is set to 1, and the A/D conversion result is
stored is stored in ADRRH and ADRRL. At the same time ADSF is cleared to 0, and the A/D
converter goes to the idle state.
3. Bit IENAD = 1, so an A/D conversion end interrupt is requested.
4. The A/D interrupt handling routine starts.
5. The A/D conversion result is read and processed.
6. The A/D interrupt handling routine ends.
If ADSF is set to 1 again afterward, A/D conversion starts and steps 2 through 6 take place.