A/D Conversion End Interrupt Request Generation Timing - NEC PD789488 User Manual

(9) Interrupt request flag (ADIF0)
Changing the contents of A/D converter mode register 0 (ADML0) does not clear the interrupt request flag
(ADIF0).
If the analog input pins are changed during A/D conversion, therefore, the A/D conversion result and the
conversion end interrupt request flag may reflect the previous analog input immediately before rewriting
ADML0. In this case, ADIF0 may already be set if it is read-accessed immediately after ADML0 is rewritten,
even when A/D conversion has not been completed for the new analog input.
In addition, when A/D conversion is restarted, ADIF0 must be cleared beforehand.
Figure 10-11. A/D Conversion End Interrupt Request Generation Timing
Rewriting ADML0
(to begin conversion
for ANIn)
A/D conversion
ADCRL0
INTAD0
Remarks 1. n = 0 to 7
2. m = 0 to 7
(10) AV pin
DD
The AV pin is used to supply power to the analog circuit. It is also used to supply power to the ANI0 to
DD
ANI7 input circuit.
If your application is designed to be changed to backup power, the AV
voltage level as the V
(11) AV pin input impedance
DD
A series resistor string of several ten of kΩ is connected between the AV
the output impedance of the reference voltage supply is high, the reference voltage supply will form a series
connection with the series resistor string, creating a large reference voltage differential.
CHAPTER 10 10-BIT A/D CONVERTER
Rewriting ADML0
(to begin conversion
for ANIm)
ANIn ANIn
ANIn
pin, as shown in Figure 10-12.
DD
Figure 10-12. AV
Main power
supply
User's Manual U15331EJ4V1UD
ADIF0 has been set, but conversion
for ANIm has not been completed.
ANIm
ANIm
ANIn ANIm
pin must be supplied with the same
DD
Pin Handling
DD
V
DD
AV
DD
Backup
capacitor
V
SS
AV
SS
and AV
DD
ANIm
pins. Consequently, if
SS
185