A-D Converter
203
Mitsubishi microcomputers
M16C / 62P Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
development
Preliminary Specifications Rev.1.0
Specifications in this manual are tentative and subject to change.
(a) Resolution Select Function
The desired resolution can be selected using the ADCON1 register’s BITS bit. If the BITS bit is set to “1”
(10-bit conversion accuracy), the A-D conversion result is stored in the ADi register (i = 0 to 7)'s bit 0 to bit
9. If the BITS bit is set to “0” (8-bit conversion accuracy), the A-D conversion result is stored in the ADi
register's bit 0 to bit 7.
(b) Sample and Hold
If the ADCON2 register’s SMP bit is set to “1” (with sample-and-hold), the conversion speed per pin is
increased to 28
AD
cycles for 8-bit resolution or 33
AD
cycles for 10-bit resolution. Sample-and-hold is
effective in all operation modes. Select whether or not to use the sample-and-hold function before starting
A-D conversion.
(c) Extended Analog Input Pins
In one-shot and repeat modes, the ANEX0 and ANEX1 pins can be used as analog input pins. Use the
ADCON1 register’s OPA1 to OPA0 bits to select whether or not use ANEX0 and ANEX1.
The A-D conversion results of ANEX0 and ANEX1 inputs are stored in the AD0 and AD1 registers,
respectively.
(d) External Operation Amp Connection Mode
Multiple analog inputs can be amplified using a single external op-amp via the ANXE0 and ANEX1 pins.
Set the ADCON1 register’s OPA1 OPA0 bits to ‘11
2
’ (external op-amp connection mode). The inputs from
ANi (i = 0 to 7)
(Note 1)
are output from the ANEX0 pin. Amplify this output with an external op-amp before
sending it back to the ANEX1 pin. The A-D conversion result is stored in the corresponding ADi register.
The A-D conversion speed depends on the response characteristics of the external op-amp. Note that the
ANXE0 and ANEX1 pins cannot be directly connected to each other. Figure 1.22.9 is an example of how
to connect the pins in external operation amp.
Note: AN
0i
and AN
2i
can be used the same as AN
i
. However, if V
CC2
< V
CC1
, do not use AN
0i
and AN
2i
as
analog input pins.
ADCON2 register's ADGSEL1 to ADGSEL0 bits=00
2
Successive conversion
register
Comparator
External op-
amp
AN
0
AN
1
AN
2
3
4
AN
5
AN
6
AN
7
ANEX0
ANEX1
00
AN
01
AN
02
AN
03
04
05
AN
06
AN
07
ADGSEL1 to ADGSEL0 bits=10
2
20
21
AN
22
AN
23
AN
24
25
26
AN
27
ADGSEL1 to ADGSEL0 bits=11
2
Resistor ladder
Microcomputer
Figure 1.22.9. External Op-amp Connection