
17. A/D Converter
17.2.5
Extended Analog Input Pins
In one-shot mode and repeat mode, ANEX0 pin or ANEX1 pin can be used as the analog input pin. Bits OPA1
and OPA0 in the AD0CON1 register select either pin. The A/D conversion result for ANEX0 input is stored
into the AD00 register, and for ANEX1 input into the AD01 register. Both results are stored into the AD00
register when the DUS bit in the AD0CON3 register is set to 1 (DMAC operating mode enabled).
Set bits APS1 and APS0 in the AD0CON2 register to 00b (AN_0 to AN_7, ANEX0, ANEX1) and the MSS bit
in the AD0CON3 register to 0 (multi-port sweep mode disabled).
17.2.6
External Operating Amplifier (Op-Amp) Connection Mode
In external op-amp connection mode, multiple analog voltage can be amplified by one external op-amp using
extended analog input pins, ANEX0 and ANEX1.
When bits OPA1 and OPA0 are set to 11b (external op-amp connection), voltage applied to pins AN_0 to AN_7
are output from ANEX0. Amplify this output signal by external op-amp and apply it to ANEX1.
Analog voltage applied to ANEX1 is converted to a digital code and the A/D conversion result is stored into the
corresponding AD0i register (i = 0 to 7). The A/D conversion rate varies depending on the response of the
external op-amp. The ANEX0 pin cannot be connected to the ANEX1 pin directly.
Set bits APS1 and APS0 to 00b (AN_0 to AN_7, ANEX0, ANEX1).
Figure 17.8 shows a connection example of external op-amp connection.
Table 17.11
Extended Analog Input Pin Settings
Figure 17.8
Connection Example in External Op-Amp Connection Mode
AD0CON1 Register
ANEX0 Function
ANEX1 Function
OPA1 Bit
OPA0 Bit
0
Not used
0
1
P9_5 as an analog input
Not used
1
0
Not used
P9_6 as an analog input
1
Output to external op-amp
Input to external op-amp
Successive conversion register
AN_0
AN_2
AN_1
AN_3
AN_4
AN_5
AN_6
AN_7
Analog input
ANEX1
External op-amp
ANEX0
Resistor ladder
Bits APS1 and APS0 in
the AD0CON2 register
00b
Comparator 0