Cautions For A/D Converter - NEC 78K0R/KE3 User Manual

10.7 Cautions for A/D Converter

(1) Operating current in STOP mode
<R>
Shift to STOP mode after clearing the A/D converter (by clearing bit 7 (ADCS) of the A/D converter mode register
(ADM) to 0). The operating current can be reduced by clearing bit 0 (ADCE) of the A/D converter mode register
(ADM) to 0 at the same time.
To restart from the standby status, clear bit 0 (ADIF) of interrupt request flag register 1L (IF1L) to 0 and start
operation.
(2) Reducing current when A/D converter is stopped
Be sure that the voltage to be applied to AV
If bit 7 (ADCS) and bit 0 (ADCE) of the A/D converter mode register (ADM) are set to 0, the current will not be
increased by the A/D converter even if a voltage is applied to AV
current flows from the power supply that supplies a voltage to AV
shown in Figure 10-25, AV
satisfying the following conditions.
Set the following states before setting AV
• Set ADCS and ADCE of the A/D converter mode register (ADM) to 0.
• Set the port mode registers (PM20 to PM27 ) of the digital I/O pins to 1 to set to input mode, or set the digital
I/O pins to low-level output (high-level output disabled) by setting the port mode registers (PM20 to PM27 )
and port registers (P20 to P27 ) to 0 to set to output mode.
• Make sure that no voltage is applied to all any of the analog or digital pins (P20/ANI0 to P27/ANI7 ) (set to 0
V).
Do not perform the following operation when AV
• Do not access the port registers (P20 to P27 ) or port mode registers (PM20 to PM27 ) by using instructions
or via DMA transfer.
Figure 10-25. Example of Circuit Where Current Flows to External Circuit
When restarting the A/D converter, operate it after the AV
(see 10.4.1 Basic operations of A/D converter for the procedure for setting the A/D converter operation).
Access digital ports after the AV
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CHAPTER 10 A/D CONVERTER
normally satisfies the conditions stated in Table 10-1.
REF
= 0 V = AV can be achieved and the external current can be reduced by
REF SS
= 0 V.
REF
= 0 V.
REF
Current flowing from power
supply supplying voltage to
AV to external circuit
REF
voltage has risen and stabilized.
REF
User's Manual U17854EJ9V0UD
, while the A/D converter is stopped. If a
REF
to an external circuit of the microcontroller as
REF
AV
REF
ANI0 to ANI7
voltage rises and stabilizes and setting ADCE = 1
REF