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Consider this example:
• AA equals 1.
• SARn equals 0x2000_0001.
• BCRn equals 0x00_00F0.
• SSIZE equals 00 (32 bits).
• DSIZE equals 01 (8 bits).
Because SSIZE > DSIZE, the source is auto-aligned. Error checking is performed on
destination registers. The access sequence is as follows:
1. Read 1 byte from 0x2000_0001, increment SARn, write 1 byte (using DARn).
2. Read 2 bytes from 0x2000_0002, increment SARn, write 2 bytes.
3. Read 4 bytes from 0x2000_0004, increment SARn, write 4 bytes.
4. Repeat 4-byte operations until SARn equals 0x2000_00F0.
5. Read byte from 0x2000_00F0, increment SARn, write byte.
If DSIZE is another size, data writes are optimized to write the largest size allowed based
on the address, but not exceeding the configured size.
21.4.5 Termination
An unsuccessful transfer can terminate for one of the following reasons:
• Error conditions—When the DMA encounters a read or write cycle that terminates
with an error condition, DSRn[BES] is set for a read and DSRn[BED] is set for a
write before the transfer is halted. If the error occurred in a write cycle, data in the
internal holding registers is lost.
• Interrupts—If DCRn[EINT] is set, the DMA drives the appropriate interrupt request
signal. The processor can read DSRn to determine whether the transfer terminated
successfully or with an error. DSRn[DONE] is then written with a 1 to clear the
interrupt, DSRn[DONE], and error status bits.
Freescale Semiconductor, Inc.
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Chapter 21 DMA Controller Module
323
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