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Rev. 1.21
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Rev. 1.21
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HT66F488/HT66F489
A/D Flash MCU with EEPROM
HT66F488/HT66F489
A/D Flash MCU with EEPROM
ADCR1 Register
Bit
7
6
5
4
3
2
1
0
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ACS4
V125E�
—
—
VREFS
ADCK2
ADCK1
ADCK�
R/W
R/W
R/W
—
—
R/W
R/W
R/W
R/W
POR
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—
—
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B
it 7
ACS4
: Selecte Internal V
BG
as ADC input Control
0: Disable
1: Enable
This bit enables V
BG
to be connected to the A/D converter. The V125EN bit must
first have been set to enable the bandgap circuit V
BG
voltage to be used by the A/D
converter. When the ACS4 bit is set high, the bandgap voltage will be routed to the A/
D converter and the other A/D input channels disconnected.
B
it 6
V125EN
: Internal V
BG
Control
0: Disable
1: Enable
This bit controls the internal Bandgap circuit on/off function to the A/D converter.
When the bit is set high the bandgap voltage V
BG
can be used by the A/D converter.
If V
BG
is not used by the A/D converter and the LVR function is disabled then the
bandgap reference circuit will be automatically switched off to conserve power. When
V
BG
is switched on for use by the A/D converter, a time t
BG
should be allowed for the
bandgap circuit to stabilise before implementing an A/D conversion.
Bit 5~4
Unimplemented, read as "0"
Bit 3
VREFS
: Selecte ADC reference voltage
0: Internal ADC power AV
DD
1: VREF
pin
This bit is used to select the reference voltage for the A/D converter. If the bit is 1 then
the A/D converter reference voltage is supplied on the external pin VREF. If the pin is
0 then the internal reference is used which is taken from the power supply pin AVDD.
When the A/D converter reference voltage is supplied on the external pin VREF which
is pin-shared with other functions, all of the other pin-shared functions on this pin are
disabled.
Bit 2 ~ 0
ADCK2 ~ ADCK0
: Select ADC clock source
000: f
SYS
001: f
SYS
/2
010: f
SYS
/4
011: f
SYS
/8
100: f
SYS
/16
101: f
SYS
/32
110: f
SYS
/64
111: Undefined
These three bits are used to select the clock source for the A/D converter.