Motorola MCF5281, MCF5282 user manual Byte Count Registers BCR0-BCR3, Bcr

Models: MCF5282 MCF5281

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DMA Controller Module Programming Model

NOTE

The DMA does not maintain coherency with the MCF5282 cache. Therefore, DMAs should not transfer data to cacheable memory unless software is used to maintain the cache coherency.

NOTE

The DMA should not be used to write data to the UART transmit FIFO in cycle steal mode. When the UART interrupt is used as a DMA request it does not negate fast enough to get a single transfer. The UART transmit FIFO only has one entry so the data from the second byte would be lost.

16.4.3 Byte Count Registers (BCR0–BCR3)

BCRn, shown in Figure 16-6and Figure 16-7,hold the number of bytes yet to be transferred for a given block. The offset within the memory map is based on the value of MPARK[BCR24BIT]. BCRn decrements on the successful completion of the address transfer of a write transfer. BCRn decrements by 1, 2, 4, or 16 for byte, word, longword, or line accesses, respectively.

Figure 16-6shows BCRn for BCR24BIT = 1.

Field

Reset

R/W Address

31

24

23

0

 

 

BCR

 

 

 

 

 

 

0000_0000_0000_0000_0000_0000

 

 

 

 

 

 

 

R/W

 

 

 

 

 

 

 

IPSBAR + 0x10C, 0x14C, 0x18C, 0x1CC

 

 

 

 

Figure 16-6. Byte Count Registers (BCRn)—BCR24BIT = 1

Figure 16-7shows BCRn for BCR24BIT = 0.

Field

Reset

R/W Address

15

0

BCR

0000_0000_0000_0000

R/W

IPSBAR + 0x10C, 0x14C, 0x18C, 0x1CC

Figure 16-7. Byte Count Registers (BCRn)—BCR24BIT = 0

DSRn[DONE], shown in Figure 16-9,is set when the block transfer is complete.

MOTOROLA

Chapter 16. DMA Controller Module

16-7

Page 347
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Motorola MCF5281, MCF5282 user manual Byte Count Registers BCR0-BCR3, Bcr