MC68HC908GR16 Datasheet, PDF (54/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Analog-to-Digital Converter (ADC)
3.8.1 ADC Status and Control Register
Function of the ADC status and control register (ADSCR) is described here.
NOTE:
Address:
Read:
Write:
Reset:
$003C
Bit 7
6
5
4
3
2
1
COCO
AIEN
ADCO ADCH4 ADCH3 ADCH2 ADCH1
0
0
0
1
1
1
1
Figure 3-4. ADC Status and Control Register (ADSCR)
Bit 0
ADCH0
1
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 except in the continuous conversion mode
where it is set after the first conversion. This bit is cleared whenever the ADSCR
is written or whenever the ADR is read.
If the AIEN bit is a logic 1, the COCO becomes a read/write bit, which should be
cleared to logic 0 for CPU to service the ADC interrupt request. Reset clears this
bit.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0)/CPU interrupt (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 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 16 ADC
channels. Only eight channels, AD7–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.
Recovery from the disabled state requires one conversion cycle to stabilize.
Data Sheet
54
Analog-to-Digital Converter (ADC)
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MC68HC908GR16 — Rev. 1.0
MOTOROLA