SAM4L Datasheet, PDF (996/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
from the Timer Busy field of the SR register (SR.TBUSY): 0 means stopped, 1 means running. In
addition when the internal timer is running, if ITIMER.ITMC is written to change the internal timer
timeout frequency, the internal counter is cleared to avoid rollover phenomena.
Note: It is possible to generate an internal timer event each GCLK period by writing 0 in
ITIMER.ITMC and by selecting the internal timer as a STRIG source
38.6.15
Peripheral DMA Controller (PDCA) Capability
There are two PDCA channels. One Rx for transferring data result to memory, and one Tx for
storing the updated configuration of the next conversion from memory.
The LCV register contains the last converted value of the sequencer according to the conversion
result format. The LCV register is updated each time the sequencer ends a conversion. If the
last converted value has not been read, there’s an overrun, the LOVR bit in the SR register indi-
cates that at least one overrun error occurred. The LOVR bit of the SR register is cleared by
writing a ‘1’ in the LOVR field of the SCR register.
Tx transfer: If the configuration is performed by the PDCA, so the CDMA register contains con-
figuration for the next conversion. If Window Mode is not used, only one word is usefull with the
MSB bit to zero. If Window Mode is used, the first word has the MSB bit to one and the second
word is dedicated for Window Mode with MSB bit set to zero.
Note: Rx PDCA transfers are 16 bits wide.
Note: In Tx, the first word received has always the same structure. The second word, if neces-
sary, has always the same structure too.
Figure 38-2. One DMA Tx transfer: No Window Mode Configuration
DMA Tx Ready
Start Of Conversion
MSB : 0
APB Data Bus
DMA Word Data
CDMA Register
DMA Word Data with MSB to "0"
31
30
0
23
22
15
14
INTERNAL
7
6
GCOMP
29
28
ZOOMRANGE
21
20
MUXNEG
13
12
TSS
RES
5
4
GAIN
27
19
11
3
STRIG
26
25
18
17
MUXPOS
10
9
2
1
BIPOLAR
24
16
8
ENSTUP
0
HWLA
42023C–SAM–02/2013
996