Buffer Types
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
14-17
14.2.11 Three-Dimensional Cyclic Buffer
A three-dimensional cyclic channel is a buffer that continues when BD_SIZE, M2D_COUNT,
and M3D_COUNT reach zero. It is defined as follows:
BD_ATTR[CONT] = 0
BD_MD_ATTR[BD] = 2
DMACHCR[xMDC] = 1
M2D_COUNT and M3D_COUNT must be set to each dimension parameter. The
M2D_OFFSET and M3D_OFFSET must be set to the next address offset for each dimension
loop. The M4D_OFFSET must be set to restore the base address of the channel. The
MxD_OFFSET is written in two’s complement. The counters of the fourth dimensions must be
cleared to zero. Figure 14-12 shows an example three-dimensional cyclic buffer.
Table 14-10. Channel Parameters Values for a Two Dimensions Cyclic Buffer
BD
BD Parameters
Value
Description
8
BD_MD_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
0x0
Do not generate interrupt when buffer ends.
CYC
0x1
Cyclic two-dimensional buffer; the third dimension offset is used
to restore the base address.
CONT
0x1
Continuous mode. The buffer does not close when
BD_MD_BSIZE and M2D_COUNT reach zero.
BTSZ
0x5
Basic transfer size is 16 bytes.
BD
0x1
Buffer dimension is 2.
CONTD
0x1
Second dimension continuous.
BD_MD_2D
M2D_COUNT
0x80
Second dimension iterations left.
M2D_BCOUNT
0x80
Second dimension base number of iterations.
M2D_OFFSET
0x1C0
Second dimension offset between two consecutive iterations.
BD_MD_3D
M3D_COUNT
0
Third dimension iterations left.
M3D_BCOUNT
0
Third dimension base number of iterations.
M3D_OFFSET
–0xF040
Third dimension offset between two consecutive iterations.
BD_MD_4D
M4D_COUNT
0
Fourth dimension iterations left.
M4D_OFFSET
0
Fourth dimension offset between two consecutive iterations.
Figure 14-12. Three-Dimensional Cyclic Buffer
0x1000
Interrupt
0x103FF
0x10400
0x1040
0xF3C0
0xF5000
0x11b0
0x1090
0x8FB0
0x8F70
0xF5040
0xFCFB0
BD8
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