
A-D CONVERTER
7905 Group User’s Manual Rev.1.0
12-2
12.1 Overview
The A-D conversion is performed in the 8-bit resolution mode or the 10-bit resolution mode. Also, the input
voltage can be compared with the set value by using the A-D converter (in other words, the comparator
function). Whether to perform the A-D conversion or comparison can be selected for each pin.
 In chapter 12, the operations common to the A-D converter’s functions (8-bit resolution, 10-bit resolution,
comparator) are simply referred to as “operation.”
Table 12.1.1 lists the performance specifications of the A-D converter.
Table 12.1.1 Performance specifications of A-D converter
Item
Performance specifications
A-D conversion method
Successive approximation conversion method
Resolution
Either of 8-bit or 10-bit resolution can be selected by software.
Absolute accuracy
8-bit resolution mode
: ±2 LSB
10-bit resolution mode
: ±3 LSB
Analog input pin (Note)
12 pins (AN0 to AN11)
Conversion rate per analog input pin
8-bit resolution mode
: 49
φAD cycles
10-bit resolution mode
: 59
φAD cycles
φAD : A-D converter’s operation clock
Note: For each of analog input pin ANi (i = 0 to 11), whether to use pin ANi as an input pin of the A-D converter or as
that of the comparator can be selected by using the comparator function select register 0 (address DC16) or the
comparator function select register 1 (address DD16).
(1) 8-bit resolution mode
The input voltage from pin ANi (i = 0 to 11) is A-D converted, and the 8-bit A-D conversion result is
stored in A-D register i. (Refer to sections “12.3 A-D conversion method” and “12.5 Comparison
voltage in 8-bit resolution mode.”)
(2) 10-bit resolution mode
The input voltage from pin ANi is A-D converted, and the 10-bit A-D conversion result is stored in
A-D register i. (Refer to section “12.3 A-D conversion method.”)
(3) Comparator function
The 8-bit value which has been set in A-D register i is compared with the voltage input from pin ANi;
and then, the result of comparison is stored into the ANi pin comparator result bit. (Refer to section
“12.6 Comparator function.”)
Comparator function Comparison operation Comparison between the set value and analog input voltage
Comparison rate per
14
φAD cycles
analog input pin