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Analog-to-Digital Converter (ADC)
NOTE:
Technical Data
236
ADCH[4:0] — ADC Channel Select Bits
ADCH[4:0] form a 5-bit field which is used to select one of the eight
ADC channels, ATD7–ATD0. The channels are detailed in
Table
14-1. Care should be taken when using a port pin as both an
analog and digital input simultaneously to prevent switching noise
from corrupting the analog signal.
The ADC subsystem is turned off when the channel select bits are all
set to 1. This feature allows for reduced power consumption for the
MCU when the ADC is not being used.
Recovery from the disabled state requires one conversion cycle to
stabilize.
The voltage levels supplied from internal reference nodes, as specified
in
Table
14-1, are used to verify the operation of the ADC converter both
in production test and for user applications.
Table 14-1. Mux Channel Select
ADCH4
ADCH3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
↓
↓
1
1
1
1
1
1
1
1
NOTE: If any unused channels are selected, the resulting ADC conversion will be unknown
or reserved.
Analog-to-Digital Converter (ADC)
ADCH2
ADCH1
ADCH0
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
0
0
↓
↓
1
0
1
0
1
1
1
1
Input Select
0
PTB0/ATD0
1
PTB1/ATD1
0
PTB2/ATD2
1
PTB3/ATD3
0
PTB4/ATD4
1
PTB5/ATD5
0
PTB6/ATD6
1
PTB7/ATD7
0
↓
Reserved
0
V
1
REFH
V
0
REFL
1
ADC power off
MC68HC908AB32
Rev. 1.0
—
MOTOROLA
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