Motorola ColdFire MCF5281 - Manual (Page 305)

DMA Controller Module
Freescale Semiconductor 16-9
27–25 BWC Bandwidth control. Indicates the number of bytes in a block transfer. When the byte count reaches a
multiple of the BWC value, the DMA releases the bus. For example, if BCR24BIT is 0, BWC is 001
(512 bytes or value of 0x0200), and BCR is 0x1000, the bus is relinquished after BCR values of
0x0E00, 0x0C00, 0x0A00, 0x0800, 0x0600, 0x0400, and 0x0200. If BCR24BIT is 0, BWC is 110, and
BCR is 33000, the bus is released after 232 bytes because the BCR is at 32768, a multiple of 16384.
24–23 — Reserved, should be cleared.
22 SINC Source increment. Controls whether a source address increments after each successful transfer.
0 No change to SAR after a successful transfer.
1 The SAR increments by 1, 2, 4, or 16, as determined by the transfer size.
21–20 SSIZE Source size. Determines the data size of the source bus cycle for the DMA control module.
00 Longword
01 Byte
10 Word
11 Line (16-byte burst)
19 DINC Destination increment. Controls whether a destination address increments after each successful
transfer.
0 No change to the DAR after a successful transfer.
1 The DAR increments by 1, 2, 4, or 16, depending upon the size of the transfer.
18–17 DSIZE Destination size. Determines the data size of the destination bus cycle for the DMA controller.
00 Longword
01 Byte
10 Word
11 Line (16-byte burst)
16 START Start transfer.
0 DMA inactive
1 The DMA begins the transfer in accordance to the values in the control registers. START is cleared
automatically after one system clock and is always read as logic 0.
Table 16-3. DCRn Field Descriptions (continued)
Bits Name Description
Encoding BCR24BIT = 0 BCR24BIT = 1
000 DMA has priority and does not negate its
request until transfer completes.
001 512 16384
010 1024 32768
011 2048 65536
100 4096 131072
101 8192 262144
110 16384 524288
111 32768 1048576
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3