SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The EDMA can efficiently extract a small frame of data from a larger frame of data. By performing a 2D-to-1D transfer, the EDMA retrieves a portion of data for the CPU to process. In this example, a 640 × 480-pixel frame of video data is stored in external memory. Each pixel is represented by a 16-bit halfword. The CPU extracts a 16 × 12-pixel subframe of the image for processing. To facilitate more efficient processing time by the CPU, the EDMA places the subframe in internal L2 SRAM. Figure 16-35 shows the transfer of a subframe from external memory to L2.
The same PaRAM entry options are used for QDMA channels, as well as DMA channels. The EDMA_TPCC_OPT_n[3] STATIC bit is set to prevent linking. For successive transfers, only changed parameters need to be programmed before triggering the channel.
Figure 16-36 shows the parameters for Subframe Extraction transfer.
(a) EDMA Parameters |
Parameter Contents | Parameter | |||||
0010 000Ch | Channel Options Parameter (OPT) | |||||
Channel Source Address (SRC) | Channel Source Address (SRC) | |||||
000Ch | 0020h | Count for 2nd Dimension (BCNT) | Count for 1st Dimension (ACNT) | |||
Channel Destination Address (DST) | Channel Destination Address (DST) | |||||
0020h | 0500h | Destination BCNT Index (DBIDX) | Source BCNT Index (SBIDX) | |||
0000h | FFFFh | BCNT Reload (BCNTRLD) | Link Address (LINK) | |||
0000h | 0000h | Destination CCNT Index (DCIDX) | Source CCNT Index (SCIDX) | |||
0000h | 0001h | Reserved | Count for 3rd Dimension (CCNT) |
(b)Channel Options Parameter (OPT) Content