
Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
A-D Converter
161
(a) Sample and hold
Sample and hold is selected by setting bit 0 of the A-D control register 2 (address 03D4
16
) to “1”. When
sample and hold is selected, the rate of conversion of each pin increases. As a result, a 28 f
AD
cycle is
achieved with 8-bit resolution and 33 f
AD
with 10-bit resolution. Sample and hold can be selected in all
modes. However, in all modes, be sure to specify before starting A-D conversion whether sample and
hold is to be used.
(b) Extended analog input pins
In one-shot mode and repeat mode, the input via the extended analog input pins ANEX0 and ANEX1 can
also be converted from analog to digital.
When bit 6 of the A-D control register 1 (address 03D7
16
) is “1” and bit 7 is “0”, input via ANEX0 is
converted from analog to digital. The result of conversion is stored in A-D register 0.
When bit 6 of the A-D control register 1 (address 03D7
16
) is “0” and bit 7 is “1”, input via ANEX1 is
converted from analog to digital. The result of conversion is stored in A-D register 1.
(c) External operation amp connection mode
In this mode, multiple external analog inputs via the extended analog input pins, ANEX0 and ANEX1, can
be amplified together by just one operation amp and used as the input for A-D conversion.
When bit 6 of the A-D control register 1 (address 03D7
16
) is “1” and bit 7 is “1”, input via AN
0
to AN
7
is
output from ANEX0. The input from ANEX1 is converted from analog to digital and the result stored in the
corresponding A-D register. The speed of A-D conversion depends on the response of the external op-
eration amp. Do not connect the ANEX0 and ANEX1 pins directly. Figure 1.20.9 is an example of how to
connect the pins in external operation amp mode.
Analog
input
External op-amp
AN
0
AN
1
AN
2
AN
3
AN
4
AN
5
AN
6
AN
7
ANEX1
ANEX0
Resistor ladder
Successive conversion register
Comparator
Figure 1.20.9. Example of external op-amp connection mode