MC68HC908AS32A Datasheet, PDF (64/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

Analog-to-Digital Converter (ADC)
ADCH[4:0] — ADC Channel Select Bits
ADCH4, ADCH3, ADCH2, ADCH1, and ADCH0 form a 5-bit field which is used to select one of 15 ADC
channels. Channel selection is detailed in the following table. Care should be taken when using a port
pin as both an analog and a digital input simultaneously to prevent switching noise from corrupting the
analog signal. See Table 3-1.
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 used. Reset sets these bits.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
Table 3-1. Mux Channel Select
ADCH4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
ADCH3
ADCH2
ADCH1
0
0
0
0
0
0
0
0
1
0
0
1
0
1
0
0
1
0
0
1
1
0
1
1
1
0
0
1
0
0
1
0
1
1
0
1
1
1
0
1
1
0
1
1
1
Range 01111 ($0F) to 11010 ($1A)
1
0
1
1
1
0
1
1
0
1
1
1
1
1
1
ADCH0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Input Select
PTB0/ATD0
PTB1/ATD1
PTB2/ATD2
PTB3/ATD3
PTB4/ATD4
PTB5/ATD5
PTB6/ATD6
PTB7/ATD7
PTD0/ATD8/ATD8
PTD1/ATD9/ATD9
PTD2/ATD10/ATD10
PTD3/ATD11/ATD11
PTD4/ATD12/TBCLK/ATD12
PTD5/ATD13/ATD13
PTD6/ATD14/TACLK/ATD14
Unused⁽¹⁾
Reserved
Unused⁽¹⁾
V_REFH(2)
V_SSA/V_REFL(2)
[ADC power off]
1. If any unused channels are selected, the resulting ADC conversion will be unknown.
2. The voltage levels supplied from internal reference nodes as specified in the table are used to
verify the operation of the ADC converter both in production test and for user applications.
MC68HC908AS32A Data Sheet, Rev. 2.0
64
Freescale Semiconductor