A-D Converter; Overview - Renesas M16C Series User Manual

M30240 Group

2.6 A-D Converter

2.6.1 Overview

The A-D converter used in the M16C/24 group operates on a successive approximation basis. The
following is an overview of the A-D converter.
2.6.1.1 Modes
The A-D converter operates in one of five modes:
(a) One-shot mode
Carries out A-D conversion on the input level on one specified pin only once.
(b) Repeat mode
Repeatedly carries out A-D conversion on the input level of one specified pin.
(c) Single-sweep mode
Carries out A-D conversion on the input level of two or more specified pins only once.
(d) Repeat sweep mode 0
Repeatedly carries out A-D conversion on the input level of two or more pins that are selected by the
A-D sweep pin select bit.
(e) Repeat sweep mode 1
Repeatedly carries out A-D conversion on the input level of two or more A-D pins. This mode is differ-
ent from the repeated sweep mode 0 in that all pins are used for A-D conversion with emphasis on the
pin or pins that are selected by the A-D sweep pin select bit.
2.6.1.2 Operation clock
The operation clock in 5 V operation can be selected from the following: fAD, divide-by-2 fAD, and
divide-by-4 fAD. The fAD frequency is equal to that of the CPU's main clock.
2.6.1.3 Conversion time
Speed of conversion for the A-D convertor varies depending on the resolution as given. Table 2.26
shows the relation between the A-D converter operation clock and conversion time.
• Sample & Hold function selected: 33 cycles for 10-bit resolution, or 28 cycles for 8-bit resolution
• No Sample & Hold function: 59 cycles for 10-bit resolution, or 49 cycles for 8-bit resolution
Table 2.26: A-D converter operation clock and conversion time
Frequency selection bit 1 (CKS1)
Frequency selection bit 0 (CKS0)
A-D converter's operation clock
Min. conversion cycles (Note 1)
Min. conversion time (Note 2)
Note 1: The number of conversion cycles per one analog input pin.
Note 2: The conversion time per one analog pin when f
Rev.1.00 Sep 24, 2003 Page 229 of 360
0
ΦAD = fAD
8-bit mode
10-bit mode
9.3 µs
8-bit mode
11.0 µs
10-bit mode
= (f(Xin) = 12 MHz)
AD
0
1
ΦAD = fAD
4 2
28 X ΦAD
33 X ΦAD
4.7 µs
5.5 µs
A-D Converter
1
Invalid
ΦAD = fAD
2.3 µs
2.8 µs