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Analog-to-Digital Converter (ADC)
NOTE:
Technical Data
94
Freescale Semiconductor, Inc.
ADCH4–ADCH0 — ADC Channel Select Bits
ADCH4–ADCH0 form a 5-bit field which is used to select one of 16
ADC channels. Only eight channels, AD7–AD0, are available on this
MCU. The channels are detailed in
when using a port pin as both an analog and digital input
simultaneously to prevent switching noise from corrupting the analog
signal.
(See Table
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
5-1, are used to verify the operation of the ADC converter both
in production test and for user applications.
Table 5-1. 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)
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Table
5-1.)
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
MC68HC908GP32
5-1. Care should be taken
Input Select
0
PTB0/AD0
1
PTB1/AD1
0
PTB2/AD2
1
PTB3/AD3
0
PTB4/AD4
1
PTB5/AD5
0
PTB6/AD6
1
PTB7/AD7
0
↓
Reserved
0
V
1
REFH
V
0
REFL
1
ADC power off
MC68HC08GP32
Rev. 6
•
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