mcf5307cft90b Freescale Semiconductor, Inc, mcf5307cft90b Datasheet - Page 295

• Manufacturer Part Number: mcf5307cft90b
• Description: Mcf5307 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

12.5.4.2 Auto-Alignment
Auto-alignment allows block transfers to occur at the optimal size based on the address,
byte count, and programmed size. To use this feature, DCR[AA] must be set. The source is
auto-aligned if SSIZE indicates a transfer size larger than DSIZE. Source alignment takes
precedence over the destination when the source and destination sizes are equal. Otherwise,
the destination is auto-aligned. The address register chosen for alignment increments
regardless of the increment value. Configuration error checking is performed on registers
not chosen for alignment.
If BCR is greater than 16, the address determines transfer size. Bytes, words, or longwords
are transferred until the address is aligned to the programmed size boundary, at which time
accesses begin using the programmed size.
If BCR is less than 16 at the start of a transfer, the number of bytes remaining dictates
transfer size. For example, AA = 1, SAR = 0x0001, BCR = 0x00F0, SSIZE = 00
(longword), and DSIZE = 01 (byte). Because SSIZE > DSIZE, the source is auto-aligned.
Error checking is performed on destination registers. The access sequence is as follows:
A[31:0], SIZ[1:0]
1. Read byte from 0x0001—write 1 byte, increment SAR.
2. Read word from 0x0002—write 2 bytes, increment SAR.
3. Read longword from 0x0004—write 4 bytes, increment SAR.
OE, BE/BWE
CSx, AS
DREQ0
D[31:0]
CLKIN
TM2
TM0
R/W
TT0
TT1
TIP
TS
TA
0
Figure 12-13. Single-Address DMA Transfer
Freescale Semiconductor, Inc.
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For More Information On This Product,
Chapter 12. DMA Controller Module
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Go to: www.freescale.com
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DMA Controller Module Functional Description
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