Buffer Types
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
14-11
Table 14-7 shows the configuration of a simple buffer designated as channel BD8. A 0x40000
(0x100
×
10
×
40) three-dimensional block is read from address 0x1000. The basic buffer is 0x40
byte. The offset between each 0x40 byte transaction is 0xF3C0 (0x10400 – 0x1040). The second
dimension parameter is 0x10. The offset between each two-dimensional buffers is –0xF3FB0
(0x1090 – 0xF5040). The channel closes when the transfer completes after 0x100 executions of
the two-dimensional buffers, and an interrupt is generated. Burst transactions are used on the bus.
14.2.8 Four-Dimensional Simple Buffer
A four-dimensional simple channel is a buffer that closes when BD_SIZE and all MxD_COUNT
reach zero. It is defined as follows:
BD_ATTR[CONT] = 0
BD_MD_ATTR[BD] = 3
DMACHCR[xMDC] = 1
All MxD_COUNT must be set to their corresponding dimension parameter. All MxD_OFFSET
must be set to the next address offset for the corresponding dimension loop. The MxD_OFFSET
is written in two’s complement. Figure 14-9 shows an example four-dimensional simple buffer.
Table 14-7. Channel Parameter Values for a Three-Dimensional Simple Buffer
BD
BD Parameters
Value
Description
8
BD_ADDR
0x1000
External memory buffer current address.
BD_MD_SIZE
0x40
Size of transfer left for this buffer.
BD_MD_BSIZE
0x40
Buffer base size of continuous buffer.
BD_MD_ATTR
SST
0x1
Generate interrupt when buffer ends.
CONT
0x0
Non-continuous mode: the channel is closed when the size
reaches zero.
CYC
0x0
Increment BD_ADDR when the size reaches zero.
BTSZ
0x7
Maximum transfer size is one burst of 64 bytes
BD
0x2
Buffer dimension is 3.
SSTD
0x2
Interrupt issued at the end of the third dimension.
CONTD 0x0
Simple
buffer.
BD_MD_2D
M2D_COUNT
0x10
Second dimension iterations left.
M2D_BCOUNT
0x10
Second dimension base number of iterations.
M2D_OFFSET
0xF3C0
Second dimension offset between two consecutive iterations.
BD_MD_3D
M3D_COUNT
0x100
Third dimension iterations left.
M3D_BCOUNT
—
Third dimension base number of iterations.
M3D_OFFSET
–0xF3FB0
Third dimension offset between two consecutive iterations of
two-dimensional buffers.
BD_MD_4D
M4D_COUNT
0
Fourth dimension iterations left.
M4D_OFFSET
0
Fourth dimension offset between two consecutive iterations.
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