916
SAM4CP [DATASHEET]
43051E–ATPL–08/14
When USEQ is set, the user can define the channel sequence to be converted by configuring ADC_SEQRx and
ADC_CHER so that channels are not interleaved during the averaging period. Under these conditions, a sample is
defined for each end of conversion as shown in
Figure 40-11, "Digital Averaging Function Waveforms on single trigger
event, non-interleaved"
.
Therefore, if the same channel is configured to be converted four times consecutively, and OSR = 1 in ADC_EMR, the
averaging result will be placed in the corresponding Channel Data register (ADC_CDRx) and Last Converted Data
register (ADC_LCDR) for each trigger event.
In such a case, the ADC effective sample rate remains the maximum ADC sample rate divided by 4 or 16, depending on
OSR.
When USEQ = 1, ASTE = 1 and OSR is different from 0, it is important to note that the user sequence must follow a
specific pattern. The user sequence must be programmed so that it generates a stream of conversion, where a given
channel is successively converted with an integer multiple depending on the value of OSR. Up to four channels can be
converted in this specific mode.
When OSR = 1, each channel to convert must be repeated four times consecutively in the sequence, so the first four
single bits enabled in ADC_CHSR must have the associated channel index programmed to the same value in
ADC_SEQ1/2. Therefore, for OSR = 1, a maximum of four channels can be converted (the user sequence allows a
maximum of 16 conversions for each trigger event).
When OSR = 2, a channel to convert must be repeated 16 times consecutively in the sequence, so all fields must be
enabled in the ADC_CHSR register, and their associated channel index programmed to the same value in
ADC_SEQ1/2. Therefore, for OSR = 2, only one channel can be converted (the user sequence allows a maximum of 16
conversions for each trigger event).
OSR = 3 and OSR = 4 are prohibited when USEQ = 1 and ASTE = 1.
Figure 40-11. Digital Averaging Function Waveforms on single trigger event, non-interleaved
ADC_EMR.OSR=1 , ASTE=1, ADC_CHSR[7:0]= 0
x
FF and ADC_MR.USEQ=1
ADC_SEQ1R = 0
x
1111_0000
Internal/E
x
ternal
Trigger event
ADC_SEL
0
ADC_CDR[1]
ADC_CDR[0]
CH0_0
ADC_LCDR
0i1
0
0
0i2 0i3
CH0_1
EOC[0]
Read ADC_CDR[0]
Read ADC_CDR[1]
CH1_1
CH0_1
EOC[1]
Read ADC_LCDR
DRDY
0 1
1
1
1
0
0
0
0
CH1_0 1i1 1i2 1i3
CH1_1
Note: 0i1,0i2,0i3, 1i1, 1i2, 1i3 are inter
m
ediate results and CH0/1_0/1 are final result of average function.