Renesas M16C/6NK Technical Information Seite 240

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Seitenansicht 239
Rev.2.10 Apr 14, 2006 page 216 of 378
REJ09B0124-0210
M16C/6N Group (M16C/6NK, M16C/6NM) 16. A/D Converter
16.2 Function
16.2.1 Resolution Select Function
The desired resolution can be selected using the BITS bit in the ADCON1 register. If the BITS bit is set to 1
(10-bit conversion accuracy), the A/D conversion result is stored in the bits 0 to 9 in the ADi register (i = 0
to 7). If the BITS bit is set to 0 (8-bit conversion accuracy), the A/D conversion result is stored in the bits
0 to 7 in the ADi register.
16.2.2 Sample and Hold
If the SMP bit in the ADCON2 register is set to 1 (with sample and hold), the conversion speed per pin is
increased to 28 φAD cycles for 8-bit resolution or 33 φAD cycles for 10-bit resolution. Sample and hold is
effective in all operating modes. Select whether or not to use the sample and hold function before starting
A/D conversion.
16.2.3 Extended Analog Input Pins
In one-shot and repeat modes, pins ANEX0 and ANEX1 can be used as analog input pins. Use bits OPA1
to OPA0 in the ADCON1 register to select whether or not use ANEX0 and ANEX1.
The A/D conversion results of ANEX0 and ANEX1 inputs are stored in registers AD0 and AD1, respectively.
16.2.4 External Operation Amplifier (Op-Amp) Connection Mode
Multiple analog inputs can be amplified using a single external op-amp via pins ANEX0 and ANEX1.
Set bits OPA1 to OPA0 in the ADCON1 register to 11b (external op-amp connection mode). The inputs
from ANi (i = 0 to 7)
(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.
Figure 16.9 shows an External Op-Amp Connection.
NOTE:
1. AN0_i and AN2_i can be used the same as ANi.
Bits ADGSEL1 to ADGSEL0 in ADCON2 register = 00b
Successive conversion
register
Comparator
External op-amp
ANEX0
ANEX1
Bits ADGSEL1 to ADGSEL0 = 10b
Bits ADGSEL1 to ADGSEL0 = 11b
Resistor ladder
MCU
AN0
AN1
AN2
AN3
AN4
AN5
AN6
AN7
AN0_0
AN0_1
AN0_2
AN0_3
AN0_4
AN0_5
AN0_6
AN0_7
AN2_0
AN2_1
AN2_2
AN2_3
AN2_4
AN2_5
AN2_6
AN2_7
Figure 16.9 External Op-Amp Connection
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