ata6616 ATMEL Corporation, ata6616 Datasheet - Page 217

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.18.3
9132A–AUTO–10/08
DRAFT
Operation
The ADC converts an analog input voltage to a 10-bit digital value through successive approxi-
mation. The minimum value represents AGND and the maximum value represents the voltage
on AVcc, the voltage reference on AREF pin or an internal 1.1V / 2.56V voltage reference.
The voltage reference for the ADC may be selected by writing to the REFS[1..0] bits in ADMUX
and AREFEN bit in AMISCR. The AVcc supply, the AREF pin or an internal 1.1V / 2.56V voltage
reference may be selected as the ADC voltage reference.
The analog input channel and differential gain are selected by writing to the MUX[4..0] bits in
ADMUX register. Any of the 11 ADC input pins ADC[10..0] can be selected as single ended
inputs to the ADC. The positive and negative inputs to the differential gain amplifier are
described in
If differential channels are selected, the differential gain stage amplifies the voltage difference
between the selected input pair by the selected gain factor 8x or 20x, according to the setting of
the MUX[4..0] bits in ADMUX register. This amplified value then becomes the analog input to the
ADC. If single ended channels are used, the gain amplifier is bypassed altogether.
The on-chip temperature sensor is selected by writing the code defined in
MUX[4..0] bits in ADMUX register when its dedicated ADC channel is used as an ADC input.
A specific ADC channel (defined in
of an external resistance flowing by a current driving by the Internal Current Source (ISRC).
The ADC is enabled by setting the ADC Enable bit, ADEN in ADCSRA register. Voltage refer-
ence and input channel selections will not go into effect until ADEN is set. The ADC does not
consume power when ADEN is cleared, so it is recommended to switch off the ADC before
entering power saving sleep modes.
The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and
ADCL. By default, the result is presented right adjusted, but can optionally be presented left
adjusted by setting the ADLAR bit in ADMUX register.
If the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read
ADCH. Otherwise, ADCL must be read first, then ADCH, to ensure that the content of the data
registers belongs to the same conversion. Once ADCL is read, ADC access to data registers is
blocked. This means that if ADCL has been read, and a conversion completes before ADCH is
read, neither register is updated and the result from the conversion is lost. When ADCH is read,
ADC access to the ADCH and ADCL Registers is re-enabled.
The ADC has its own interrupt which can be triggered when a conversion completes. When ADC
access to the data registers is prohibited between reading of ADCH and ADCL, the interrupt will
trigger even if the result is lost.
Table
4-58.
ATA6616/ATA6617 [Preliminary]
Table
4-58) is used to measure the voltage to the boundaries
Table 4-58
to the
217