MC908AB32CFUE Datasheet, PDF (236/392 Pages) Freescale Semiconductor, Inc – Microcontrollers

Analog-to-Digital Converter (ADC)
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.
NOTE: 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 ADCH2 ADCH1 ADCH0
Input Select
0
0
0
0
0
PTB0/ATD0
0
0
0
0
1
PTB1/ATD1
0
0
0
1
0
PTB2/ATD2
0
0
0
1
1
PTB3/ATD3
0
0
1
0
0
PTB4/ATD4
0
0
1
0
1
PTB5/ATD5
0
0
1
1
0
PTB6/ATD6
0
0
1
1
1
PTB7/ATD7
0
1
0
0
0
↓
↓
↓
↓
↓
Reserved
1
1
1
0
0
1
1
1
0
1
V_REFH
1
1
1
1
0
V_REFL
1
1
1
1
1
ADC power off
NOTE: If any unused channels are selected, the resulting ADC conversion will be unknown
or reserved.
Technical Data
236
Analog-to-Digital Converter (ADC)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor