MC68HC908QY4_10 Datasheet, PDF (46/168 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Analog-to-Digital Converter (ADC)
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when ADR is read or ADSCR is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update ADR 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
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 3-1. 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 1.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
Table 3-1. MUX Channel Select
CH4 CH3 CH2 CH1 CH0
0
0
0
0
0
0
0
0
0
1
0
0
0
1
0
0
0
0
1
1
0
0
1
0
0
↓
↓
↓
↓
↓
1
1
0
1
0
1
1
0
1
1
1
1
1
0
0
1
1
1
0
1
1
1
1
1
0
1
1
1
1
1
ADC
Channel
ADC0
ADC1
ADC2
ADC3
—
—
—
—
—
—
—
—
Input Select
PTA0
PTA1
PTA4
PTA5
Unused⁽¹⁾
Reserved
Unused
V_DDA(2)
V_SSA(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 produc-
tion test and for user applications.
MC68HC908QY/QT Family Data Sheet, Rev. 6
46
Freescale Semiconductor