CC2430 Datasheet, PDF (86/234 Pages) Texas Instruments – A True System-on-Chip solution for 2.4 GHz IEEE 802.15.4 / ZigBee-TM

CC2430
13.2 DMA Controller
The CC2430 includes a direct memory access
(DMA) controller, which can be used to relieve
the 8051 CPU core of handling data
movement operations thus achieving high
overall performance with good power
efficiency. The DMA controller can move data
from a peripheral unit such as ADC or RF
transceiver to memory with minimum CPU
intervention.
The DMA controller coordinates all DMA
transfers, ensuring that DMA requests are
prioritized appropriately relative to each other
and CPU memory access. The DMA controller
contains a number of programmable DMA
channels for memory-memory data movement.
The DMA controller controls data transfers
over the entire address range in XDATA
memory space. Since most of the SFR
registers are mapped into the DMA memory
space, these flexible DMA channels can be
used to unburden the CPU in innovative ways,
e.g. feed a USART with data from memory or
periodically transfer samples between ADC
and memory, etc. Use of the DMA can also
reduce system power consumption by keeping
the CPU in a low-power mode without having
to wake up to move data to or from a
peripheral unit. Note that section 12.4
describes which SFR registers that are not
mapped into XDATA memory space.
The main features of the DMA controller are as
follows:
• Five independent DMA channels
• Three configurable levels of DMA
channel priority
• 31 configurable transfer trigger events
• Independent control of source and
destination address
• Single, block and repeated transfer
modes
• Supports length field in transfer data
setting variable transfer length
• Can operate in either word-size or
byte-size mode
13.2.1 DMA Operation
There are five DMA channels available in the
DMA controller numbered channel 0 to
channel 4. Each DMA channel can move data
from one place within the DMA memory space
to another i.e. between XDATA locations.
In order to use a DMA channel it must first be
configured as described in sections 13.2.2 and
13.2.3. Figure 17 shows the DMA state
diagram.
Once a DMA channel has been configured it
must be armed before any transfers are
allowed to be initiated. A DMA channel is
armed by setting the appropriate bit in the
DMA Channel Arm register DMAARM.
When a DMA channel is armed a transfer will
begin when the configured DMA trigger event
occurs. There are 31 possible DMA trigger
events, e.g. UART transfer, Timer overflow
etc. The trigger event to be used by a DMA
channel is set by the DMA channel
configuration. The DMA trigger events are
listed in Table 37.
In addition to starting a DMA transfer through
the DMA trigger events, the user software may
force a DMA transfer to begin by setting the
corresponding DMAREQ bit.
CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A
Page 86 of 232