Table 22-3. Modes of operation
Mode Description
Normal In Normal mode, the eDMA transfers data between a source and a destination. The source and
destination can be a memory block or an I/O block capable of operation with the eDMA.
A service request initiates a transfer of a specific number of bytes (NBYTES) as specified in the
transfer control descriptor (TCD). The minor loop is the sequence of read-write operations that
transfers these NBYTES per service request. Each service request executes one iteration of the
major loop, which transfers NBYTES of data.
Debug DMA operation is configurable in Debug mode via the control register:
• If CR[EDBG] is cleared, the DMA continues to operate.
• If CR[EDBG] is set, the eDMA stops transferring data. If Debug mode is entered while a
channel is active, the eDMA continues operation until the channel retires.
Wait Before entering Wait mode, the DMA attempts to complete its current transfer. After the transfer
completes, the device enters Wait mode.
22.3 Memory map/register definition
The eDMA's programming model is partitioned into two regions:
• The first region defines a number of registers providing control functions
• The second region corresponds to the local transfer control descriptor (TCD)
memory
22.3.1
TCD memory
Each channel requires a 32-byte transfer control descriptor for defining the desired data
movement operation. The channel descriptors are stored in the local memory in
sequential order: channel 0, channel 1, ... channel 15. Each TCDn definition is presented
as 11 registers of 16 or 32 bits.
22.3.2
TCD initialization
Prior to activating a channel, you must initialize its TCD with the appropriate transfer
profile.
Chapter 22 Enhanced Direct Memory Access (eDMA)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 429
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