MC908GR32AVFAE Datasheet, PDF (66/314 Pages) Freescale Semiconductor, Inc – 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 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 completed between writes to the ADSCR 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 one of 32 ADC channels. Only 24 channels,
AD23–AD0, are available on this MCU. The channels are detailed in Table 3-1. Care should be taken
when using a port pin as both an analog and 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 being 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 converter both in production test and for user
applications.
Table 3-1. Mux Channel Select⁽¹⁾
ADCH4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ADCH3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
ADCH2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
ADCH1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
ADCH0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Input Select
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/AD4
PTB5/AD5
PTB6/AD6
PTB7/AD7
PTA0/KBD0/AD8
PTA1/KBD1/AD9
PTA2/KBD2/AD10
PTA3/KBD3/AD11
PTA4/KBD4/AD12
PTA5/KBD5/AD13
PTA6/KBD6/AD14
PTA7/KBD7/AD15
Continued on next page
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
66
Freescale Semiconductor