Buffer Types
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
14-7
14.2.5 One-Dimensional Complex Buffers With Dual Cyclic Buffers
Any combination of the previously described buffers can be used. Dual cyclic buffers, which use
two areas in memory to store data, constitute a useful combination of buffer types. While one
area of memory is processed, the other receives new data, as shown in Figure 14-6.
Figure 14-6. Dual Cyclic Buffers
Buffer 0 starts at address 0x1000, and transfers 0x200 byte-blocks. Buffer 1 starts at address
0x2000 and transfer size is also 0x200 bytes. Table 14-5 lists the channel parameter values
corresponding to dual cyclic buffers.
Table 14-5. Channel Parameter Values for Dual Cyclic Buffers
BD
BD Parameters
Value
Description
0
BD_ADDR
0x1000
External memory buffer current address.
BD_SIZE
0x200
Size of transfer left for this buffer.
BD_BSIZE
0x200
Buffer base size of cyclic buffer.
BD_ATTR
CONT
0x1
Continuous mode. Do not shut down the channel when size reaches zero.
CYC
0x1
Reinitialize BD_ADDRESS to original value when size reaches zero.
NBD
0x1
When size reaches zero, next request calls buffer 1.
BTSZ
0x7
Maximum transfer size is one burst of 64 bytes.
1
BD_ADDR
0x2000
External memory buffer current address.
BD_SIZE
0x200
Size of transfer left for this buffer.
BD_BSIZE
0x200
Buffer base size of cyclic buffer.
BD_ATTR
SST
0x1
Generate interrupt when buffer ends
CONT
0x1
Continuous mode. Do not shut down the channel when size reaches zero
CYC
0x1
Reinitialize BD_ADDRESS to original value when size reaches zero
NBD
0x0
When size reaches zero, the next request calls buffer 0
BTSZ
0x7
Maximum transfer size is one burst of 64 bytes
0x1000
0x11F8
0x2000
0x21F8
Interrupt
BD0
BD1
Summary of Contents for MSC8144E
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