MC68HC908KX8 Datasheet, PDF (252/310 Pages) Motorola, Inc – Microcontrollers

Analog-to-Digital Converter (ADC)
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the
ADR register at the end of each conversion. Only one conversion is
allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH4–ADCH0 — ADC Channel Select Bits
ADCH4–ADCH0 form a 5-bit field which is used to select the input for
the A/D measurement. The choices are one of four ADC channels, as
well as V_REFH and V_SS. Input selection is detailed in Table 17-1. 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.
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 17-1. Mux Channel Select
ADCH4 ADCH3 ADCH2 ADCH1 ADCH0
Input Select
0
0
0
0
0
PTB0
0
0
0
0
1
PTB1
0
0
0
1
0
PTB2
0
0
0
1
1
PTB3
0
0
1
0
0
Unused⁽¹⁾
~
~
~
~
~
~
1
1
1
0
0
Unused ⁽¹⁾
1
1
1
0
1
V_REFH(2)
1
1
1
1
0
V_SSAD ⁽²⁾
1
1
1
1
1
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 applica-
tions.
Technical Data
252
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
Analog-to-Digital Converter (ADC)
MOTOROLA