Datasheet

MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
158 Analog-to-Digital Converter (ADC) MOTOROLA
Analog-to-Digital Converter (ADC)
NON-DISCLOSURE AGREEMENT REQUIRED
CH[4:0] — ADC Channel Select Bits
CH4, CH3, CH2, CH1, and CH0 form a 5-bit field which is used to
select one of the four ADC channels. The five select bits are detailed
in Table 11-1. 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 all of these bits to a
logic 1.
NOTE: Recovery from the disabled state requires one conversion cycle to
stabilize.
Table 11-1. MUX Channel Select
CH4 CH3 CH2 CH1 CH0
ADC
Channel
Input Select
00000 ADC0 PTA0
00001 ADC1 PTA1
00010 ADC2 PTA4
00011 ADC3 PTA5
00100 —
Unused
(1)
1. If any unused channels are selected, the resulting ADC conversion will be unknown.
↓↓↓↓↓ —
11010 —
11011 — Reserved
11
1 0 0 — Unused
11
1 0 1 —
V
DDA
(2)
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.
111 1 0 —
V
SSA
(2)
111 1 1 — ADC power off