A/D Conversion Method, 8-Bit Mode - Renesas M16C Series User Manual

M30240 Group

2.6.4.2 A/D Conversion method, 8-bit mode

In 8-bit mode, the 8 higher-order bits of the 10-bit successive comparison register becomes the A-D
conversion result. Hence, if compared to a result obtained by using an 8-bit A-D converter, the voltage
compared is different by 3 Vref/2048 (see underscored in Table 2.33), and differences in stepping points
of output codes occur as shown in Figure 2.94.
Table 2.35: Comparison voltage of 8-bit mode to 8-bit A-D converter
Comparison voltage Vref
Optimal conversion characteristics of 8-bit A-D converter (V
(Result of A-D conversion)
Optimal conversion characteristics in 8-bit mode (V
(Result of A-D conversion)
Figure 2.94: Conversion level characteristics between 8-bit mode and 8-bit A-D converter
Rev.1.00 Sep 24, 2003 Page 248 of 360
n = 0
n = 1 to 255
Output code
02
01
00
10
Output code
(Note)
8-bit 10-bit
mode mode
09
02
08
07
06
05
01
04
03
02
01
00
00
17.5
Note: Differences in stepping points of output code for analog input voltage.
8-bit mode
0
V x n - V x 0.5
REF REF
8 10
2 2
= 5.12 V)
REF
30
Analog input voltage (mV)
= 5.12 V)
REF
10bit-mode
8bit-mode
37.5
Analog input voltage (mV)
A-D Converter
8-bit A-D converter
0
V x n - V x 0.5
REF REF
8 8
2 2