AN2108 Freescale Semiconductor / Motorola, AN2108 Datasheet - Page 14

• Manufacturer Part Number: AN2108
• Description: AN2108 Programming the DSP56307/DSP56311 EFCOP in C Using Taskings Tool Suite
• Manufacturer: Freescale Semiconductor / Motorola

4.2.1 EFCOP DMA Input
14
Transferring Data to and from the EFCOP
The appropriate DMA channel should be set to respond to requests from MDRQ11 or MDRQ12,
as required. The EFCOP always
DMA transfer occurs only if the appropriate DMA channel is configured to respond to such a request. If
DMA transfers are used for both input and output, two DMA channels are required.
The DMA controller cannot be used to access memory locations below 4K ($1000), since the EFCOP uses
this memory area for its coefficient and data buffers (FCM and FDM). This is true even when the EFCOP
is not used. Memory below 4K is connected to the EFCOP instead of the on-device DMA controller, so
only the EFCOP or the DSP56300 core can assess it.
For the application discussed here, four words are written to the FDIR each time. A two-dimensional (2-D)
DMA transfer to the EFCOP is also used. This type of transfer moves four words into the FDIR on each
DMA request (as shown in Figure 7). A 1-D DMA channel could also be used without penalty (see [4]).
Using a 2-D DMA transfer, four words are transmitted each time a trigger from the EFCOP is received
until the length of the input sequence is reached. The only “trick” is to set the DMA offset register, DORx,
to one. The configuration principles behind this 2-D transfer are as follows:
4. For details on DMA, refer to [4] and [5].
•
•
•
DMA Control Register (DCR):
— DMA Transfer Mode (DTM) = line transfer triggered by request
— DMA Request Source (DRS) = MDRQ11 (see Table 3-4)
— DMA Address Mode (DAM)
DMA Counter Register (DCO):
— in mode B: DCOL=3, DCOH= ((number of 4-word blocks required)-1)
DMA Offset Register (DOR0): set to 1.
— Source, 2-D counter mode B, offset DOR0
— Destination. No update, no offset7
+DOR0
+1
+1
+1
+1
+1
+1
Input samples
X/Y Memory
Programming the DSP56307/DSP56311 EFCOP in C
Figure 7. Four-Word Deep FDIR Access Using DMA
x(0)
x(1)
x(2)
x(3)
x(4)
x(5)
...
...
Freescale Semiconductor, Inc.
For More Information On This Product,
generates DMA requests when FDIBE or FDOBF are set. However, a
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4
FDIR
Transfer to FDM
EFCOP