MC68HC908GZ8 Datasheet, PDF (72/344 Pages) Motorola, Inc – Microcontrollers

Analog-to-Digital Converter (ADC)
NOTE:
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 Table 5-1. 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. See Table 5-1.
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⁽¹⁾
ADCH4 ADCH3 ADCH2 ADCH1 ADCH0
Input Select
0
0
0
0
0
PTB0/AD0
0
0
0
0
1
PTB1/AD1
0
0
0
1
0
PTB2/AD2
0
0
0
1
1
PTB3/AD3
0
0
1
0
0
PTB4/AD4
0
0
1
0
1
PTB5/AD5
0
0
1
1
0
PTB6/AD6
0
0
1
1
1
PTB7/AD7
0
1
0
0
0
↓
↓
↓
↓
↓
Unused
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
1. If any unused channels are selected, the resulting ADC conversion will be unknown or re-
served.
Data Sheet
72
Analog-to-Digital Converter (ADC)
MC68HC908GZ8
Freescale Semiconductor