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R8C/38T-A Group
23. A/D Converter
Under development Preliminary document
Specifications in this document are tentative and subject to change.
R01UH0241EJ0010 Rev.0.10
Page 549 of 730
Aug 05, 2011
23.2.6
A/D Control Register 1 (ADCON1)
Notes:
1. When the 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 VREFMON bit in the OCVREFCR register to 1 (on-chip reference voltage and
analog input are connected).
When the on-chip reference voltage is not used as analog input, first set the VREFMON 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 (on-chip reference voltage selected) in single sweep mode or repeat sweep mode.
3. When the ADEX0 bit is 1 (on-chip reference voltage selected), the settings of bits CH0 to CH2 in the ADINSEL
register and bits ADGSEL0 and ADGSEL1 (analog input AN0 to AN19 selected) are disabled, and on-chip
reference voltage is selected. When on-chip reference voltage is used, set bits CH2 to CH0 in the ADINSEL
register to 000b.
.
4. When the on-chip reference voltage is used (ADEX0 = 1), set the ADDDAEN bit to 0 (A/D open-circuit detection
assist function disabled).
5. When the ADSTBY bit is changed from 0 (A/D operation stops) to 1 (A/D operation enabled), wait for one
AD
cycle or more before starting A/D conversion.
6. 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 according to external circuits. Careful evaluation should be
performed according to the system before using this function.
7. When bits ADDDAEN and ADDDAEL are rewritten, allow at least one cycle of fAD to elapse before starting A/D
conversion.
If the ADCON1 register is rewritten during A/D conversion, the conversion result is undefined.
Address 00217h
Bit
b7
b6
b5b4b3
b2b1b0
After Reset
0
00
0000
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, 3, 4)R/W
b1
—
Reserved
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
0: A/D operation stops (standby)
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