
R8C/3GM Group
27. A/D Converter
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
27.2.6
A/D Control Register 1 (ADCON1)
Notes:
1. When on-chip reference voltage is used as analog input, first set the ADEX0 bit to 1 (on-chip reference voltage
selected) and then set the OCVREFAN bit in the OCVREFCR register to 1 (on-chip reference voltage and analog
input are connected).
When on-chip reference voltage is not used as analog input, first set the OCVREFAN bit to 0 (on-chip reference
voltage and analog input are cut off) and then set the ADEX0 bit to 0 (extended analog input pin not selected).
2. Do not set to 1 (A/D conversion using comparison reference voltage as input) in single sweep mode or repeat
sweep mode.
3. When the ADSTBY bit is changed from 0 (A/D operation stops) to 1 (A/D operation enabled), wait for 1
φAD cycle
or more before starting A/D conversion.
4. Stop the A/D function before setting to standby. When the ADSBY bit is set to 1 (standby), any access to the A/D
associated registers (addresses 00C0h to 00CFh, and 00D4h to 00D7h) is disabled.
5. To enable the A/D open-circuit detection assist function, select the conversion start state with the ADDDAEL bit
after setting the ADDDAEN bit to 1 (enabled).
The conversion result with an open circuit varies with external circuits. Careful evaluation should be performed
according to the system before using this function.
6. When on-chip reference voltage is used (ADEX0 = 1), set bits CH2 to CH0 in the ADINSEL register to 000b.
7. When on-chip reference voltage is used (ADEX0 = 1), set the ADDDAEN bit to 0 (A/D open-circuit detection
assist function disabled).
If the ADCON1 register is rewritten during A/D conversion, the conversion result is undefined.
Address 00D7h
Bit
b7
b6
b5
b4b3b2
b1b0
After Reset
0
000
00
Bit
Symbol
Bit Name
Function
R/W
b0
ADEX0
Extended analog input pin select bit
(1) 0: Extended analog input pin not selected
1: On-chip reference voltage selected
(2, 6, 7)R/W
b1
—
Reserved bits
Set to 0.
R/W
b2
—
b3
—
b4
BITS
8/10-bit mode select bit
0: 8-bit mode
1: 10-bit mode
R/W
b5
ADSTBY A/D standby bit
(3)0: A/D operation stops (standby)
(4)1: A/D operation enabled
R/W
b6
ADDDAEN A/D open-circuit detection assist
0: Disabled
1: Enabled
R/W
b7
ADDDAEL A/D open-circuit detection assist
0: Discharge before conversion
1: Precharge before conversion
R/W