ata6616 ATMEL Corporation, ata6616 Datasheet - Page 218

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

4.18.4
218
ATA6616/ATA6617 [Preliminary]
Starting a Conversion
A single conversion is started by writing a logical one to the ADC Start Conversion bit, ADSC.
This bit stays high as long as the conversion is in progress and will be cleared by hardware
when the conversion is completed. If a different data channel is selected while a conversion is in
progress, the ADC will finish the current conversion before performing the channel change.
Alternatively, a conversion can be triggered automatically by various sources. Auto Triggering is
enabled by setting the ADC Auto Trigger Enable bit, ADATE in ADCSRA register. The trigger
source is selected by setting the ADC Trigger Select bits, ADTS in ADCSRB register (see
description of the ADTS bits for a list of the trigger sources). When a positive edge occurs on the
selected trigger signal, the ADC prescaler is reset and a conversion is started. This provides a
method of starting conversions at fixed intervals. If the trigger signal still is set when the conver-
sion completes, a new conversion will not be started. If another positive edge occurs on the
trigger signal during conversion, the edge will be ignored. Note that an Interrupt Flag will be set
even if the specific interrupt is disabled or the Global Interrupt Enable bit in SREG register is
cleared. A conversion can thus be triggered without causing an interrupt. However, the Interrupt
Flag must be cleared in order to trigger a new conversion at the next interrupt event.
Figure 4-83. ADC Auto Trigger Logic
Using the ADC Interrupt Flag as a trigger source makes the ADC start a new conversion as soon
as the ongoing conversion has finished. The ADC then operates in Free Running mode, con-
stantly sampling and updating the ADC Data Register. The first conversion must be started by
writing a logical one to the ADSC bit in ADCSRA register. In this mode the ADC will perform suc-
cessive conversions independently of whether the ADC Interrupt Flag, ADIF is cleared or not.
If Auto Triggering is enabled, single conversions can be started by writing ADSC in ADCSRA
register to one. ADSC can also be used to determine if a conversion is in progress. The ADSC
bit will be read as one during a conversion, independently of how the conversion was started.
SOURCE 1
SOURCE n
. . .
. . .
. . .
. . .
ADSC
ADIF
ADTS[2:0]
Detector
Edge
ADATE
DRAFT
Start
ADC Prescaler
Conversion
CLK
Logic
9132A–AUTO–10/08
CLK
IO
ADC