CC1110Fx / CC1111Fx
12.5.2
DMA Configuration Parameters
Variable Length Transfer Count: When
VLEN≠000 and VLEN≠111, the transfer count
is given by the value of the first byte/word in
source data, n, + a constant given by the
VLEN setting. This allows for variable length
transfer count.
Setup and control of the DMA operation is
performed by the user software. This section
describes the parameters which must be
configured before a DMA channel can be
used. Section 12.5.3 on Page 105 describes
how the parameters are set up in software and
passed to the DMA controller.
Note: For byte size transfers (see Section
12.5.2.4), n is defined as the first byte in
source data or the 7 LSB of the first byte in
source data, depending on the M8 setting
(see Section 12.5.2.9). For word size
transfers, n is the 13 LSB of the first word
in source data.
The behavior of each of the five DMA
channels is configured with the following
parameters:
12.5.2.1 Source Address (SRCADDR)
There are four possible configurations:
The address of the location in XDATA memory
space where the DMA channel shall start to
read data.
1. VLEN=001
Transfer
commanded by n + 1
number
of
of
of
of
bytes/words
bytes/words
bytes/words
bytes/words
12.5.2.2 Destination Address (DESTADDR)
2. VLEN=010
The address of the location in XDATA memory
space where the DMA channel will write the
data read from the source address. The user
must ensure that the destination is writable.
Transfer
commanded by n
number
3. VLEN=011
Transfer
commanded by n + 2
number
12.5.2.3 Transfer Count
The number of bytes/words needed to be
moved from source to destination. When the
transfer count is reached, the DMA controller
rearms or disarms the DMA channel
(depending on transfer mode) and alert the
CPU by setting the DMAIRQ.DMAIFn bit to 1.
If IRQMASK=1, IRCON.DMAIF will also be set
and an interrupt request is generated if
IEN1.DMAIE=1. The transfer count can be of
fixed or variable length depending on how the
DMA channel is configured.
4. VLEN=100
Transfer
number
commanded by n + 3
For all of the above configurations, the transfer
count will be limited to LEN bytes/words when
n ≥ LEN. In cases where n < LEN, the transfer
count is given by the VLENsetting. This means
that when VLEN=010, LEN should be equal to
nmax, while in the other three cases, LEN
should be set to nmax + 1.
Fixed Length Transfer Count: When
VLEN=000or VLEN=111, the transfer count is
set by the LENsetting.
Figure 27 shows the different VLENoptions.
SWRS033H
Page 103 of 246
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