deveopmen
A-D Converter
Preliminary Specifications REV.B
Specifications in this manual are tentative and subject to change.
Mitsubishi microcomputers
M16C/80 (144-pin version) group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
171
(a) Sample and hold
Sample and hold is selected by setting bit 0 of the A-D control register 2 (address 0394
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 ANEX
0
and ANEX
1
can
also be converted from analog to digital.
When bit 6 of the A-D control register 1 (address 0397
16
) is “1” and bit 7 is “0”, input via ANEX
0
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 0397
16
) is “0” and bit 7 is “1”, input via ANEX
1
is
converted from analog to digital. The result of conversion is stored in A-D register 1.
Set the related input peripheral function of the function select register B3 to disabled.
(c) External operation amp connection mode
In this mode, multiple external analog inputs via the extended analog input pins, ANEX
0
and ANEX
1
, 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 0397
16
) is “1” and bit 7 is “1”, input via AN
0
to AN
7
is
output from ANEX
0
. The input from ANEX
1
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 ANEX
0
and ANEX
1
pins directly. Figure 1.21.9 is an example of how to
connect the pins in external operation amp mode.
Set the related input peripheral function of the function select register B3 to disabled.
Analog
input
External op-amp
AN
0
AN
1
AN
2
AN
3
AN
4
AN
5
AN
6
AN
7
ANEX1
ANEX0
Resistance ladder
Successive conversion register
Comparator
Figure 1.21.9. Example of external op-amp connection mode