MC68HC908EY16 Datasheet, PDF (50/278 Pages) Motorola, Inc – Microcontrollers

Analog-to-Digital Converter (ADC) Module
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 the data register is read or the status/control register 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 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
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 8 ADC
channels. The ADC channels are detailed in Table 3-1.
NOTE
Take care to prevent switching noise from corrupting the analog signal
when simultaneously using a port pin as both an analog and digital input.
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.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
The voltage levels supplied from internal reference nodes as specified in
Table 3-1 are used to verify the operation of the ADC both in production test and for user applications.
Table 3-1. 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
PTB4
0
0
1
0
1
PTB5
0
0
1
1
0
PTB6
0
0
1
1
1
PTB7
0
1
0
0
0
to
Unused *
1
1
0
1
0
1
1
0
1
1
Reserved **
1
1
1
0
0
Unused *
1
1
1
0
1
V_REFH
1
1
1
1
0
V_REFL
1
1
1
1
1
ADC power off
* If any unused channels are selected, the resulting ADC conversion will be unknown.
** Used for factory testing.
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
50
Freescale Semiconductor