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CHAPTER 12 A/D CONVERTER
User’s Manual U19780EJ2V0UD
332
(3) Analog conference voltage control register (ADVRC)
This register is used to select the source of the negative reference voltage for the A/D converter.
The electrical characteristics of the A/D converter can be maintained even in low-voltage mode by enabling operation
of the A/D converter's input gate voltage booster.ADVRC can be set by a 1-bit or 8-bit memory manipulation
instruction.
Reset signal generation clears this register to 00H.
Figure 12-7. Format of Analog Conference Voltage Control Register (ADVRC)
Address: FF2EH After reset: 00H R/W
Symbol
7 6 5 4 3 2 1 0
ADVRC ADREF
Note 1
0
0
0
0
0 VRGV
Note 2
0
ADREF
Note 1
Negative reference voltage for the A/D converter selection
0 AV
SS
1 AV
REFM
(external conference voltage input)
VRGV
Note 2
A/D converter booster circuit operation control
0 Stop
operation
1 Enables
operation
Notes 1
.
As the AV
REFM
is not mounted on 78K0/KB2-A, Clear the ADREF to 0.
2.
When using the A/D converter in normal mode 2 (LV1 = 0, LV0 = 1) or low-voltage mode (LV1 = 1, LV0
= 0), enable A/D conversion (by setting ADCE to 1) after starting up the A/D converter voltage booster
(by setting VRGV to 1) and waiting for the reference voltage stabilization time (10
μ
s) to elapse. Note
that it takes the A/D voltage comparator 1
μ
s to stabilize after being enabled. The validity of the data
converted first can therefore be improved by enabling A/D conversion (by setting ADCS to 1) at least 1
μ
s after enabling the A/D voltage comparator. If A/D conversion is enabled without waiting for at least 1
μ
s, ignore the data converted first.