DMA_DCRn field descriptions (continued)
Field Description
10 16-bit
11 Reserved (generates a configuration error (DSRn[CE]) if incorrectly specified at time of channel
activation)
16
START
Start transfer
0 DMA inactive
1 The DMA begins the transfer in accordance to the values in the TCDn. START is cleared
automatically after one module clock and always reads as logic 0.
15–12
SMOD
Source address modulo
Defines the size of the source data circular buffer used by the DMA Controller. If enabled (SMOD is non-
zero), the buffer base address is located on a boundary of the buffer size. The value of this boundary is
based upon the initial source address (SAR). The base address should be aligned to a 0-modulo-(circular
buffer size) boundary. Misaligned buffers are not possible. The boundary is forced to the value determined
by the upper address bits in the field selection.
0000 Buffer disabled
0001 Circular buffer size is 16 bytes
0010 Circular buffer size is 32 bytes
0011 Circular buffer size is 64 bytes
0100 Circular buffer size is 128 bytes
0101 Circular buffer size is 256 bytes
0110 Circular buffer size is 512 bytes
0111 Circular buffer size is 1 KB
1000 Circular buffer size is 2 KB
1001 Circular buffer size is 4 KB
1010 Circular buffer size is 8 KB
1011 Circular buffer size is 16 KB
1100 Circular buffer size is 32 KB
1101 Circular buffer size is 64 KB
1110 Circular buffer size is 128 KB
1111 Circular buffer size is 256 KB
11–8
DMOD
Destination address modulo
Defines the size of the destination data circular buffer used by the DMA Controller. If enabled (DMOD
value is non-zero), the buffer base address is located on a boundary of the buffer size. The value of this
boundary depends on the initial destination address (DAR). The base address should be aligned to a 0-
modulo-(circular buffer size) boundary. Misaligned buffers are not possible. The boundary is forced to the
value determined by the upper address bits in the field selection.
0000 Buffer disabled
0001 Circular buffer size is 16 bytes
0010 Circular buffer size is 32 bytes
0011 Circular buffer size is 64 bytes
0100 Circular buffer size is 128 bytes
0101 Circular buffer size is 256 bytes
0110 Circular buffer size is 512 bytes
0111 Circular buffer size is 1 KB
1000 Circular buffer size is 2 KB
1001 Circular buffer size is 4 KB
Table continues on the next page...
Chapter 23 DMA Controller Module
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 359
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