MC68HC908AT32 Datasheet, PDF (311/378 Pages) Freescale Semiconductor, Inc – Microcontrollers

I/O Registers
COCO — Conversions Complete Bit
When the AIEN bit is a logic 0, the COCO is a read-only bit which is set each time a conversion is
completed. This bit is cleared whenever the ADC status and control register is written or whenever the
ADC data register is read.
If the AIEN bit is a logic 1, the COCO is a read/write bit which selects the CPU to service the ADC
interrupt request. Reset clears this bit.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0)
or
1 = DMA interrupt enabled (AIEN = 1)
0 = CPU interrupt enabled (AIEN = 1)
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 15 ADC
channels. The six channels are detailed in the following table. 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. (See Table 26-1.)
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 used. Reset sets these bits.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
ADCH4
0
0
0
0
0
0
0
0
0
0
Table 26-1. MUX Channel Select
ADCH3
0
0
0
0
0
0
0
0
1
1
ADCH2
0
0
0
0
1
1
1
1
0
0
ADCH1
0
0
1
1
0
0
1
1
0
0
ADCH0
0
1
0
1
0
1
0
1
0
1
Input Select
PTB0/ATD0
PTB1/ATD1
PTB2/ATD2
PTB3/ATD3
PTB4/ATD4
PTB5/ATD5
PTB6/ATD6
PTB7/ATD7
PTD0/ATD8
PTD1/ATD9
Continued on next page
MC68HC908AT32 Data Sheet, Rev. 3.1
Freescale Semiconductor
311