SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Higher bandwidth applications require that multiple data elements be presented to the processor core for every synchronization event. This frame of data can either be from multiple sources that are working simultaneously or from a single high-throughput peripheral that streams data to/from the processor.
In this example, a port is receiving a video frame from a camera and presenting it to the DSP one array at a time. The video image is 640 × 480 pixels, with each pixel represented by a 16-bit element. The image is to be stored in external memory.
To transfer data from an external peripheral to an external buffer one array at a time based on EVTn , channel n must be configured. Due to the nature of the data (a video frame made up of arrays of pixels) the destination is essentially a 2D entity. Figure 16-42 shows the parameters to service the incoming data with a 1D-to-2D transfer using AB-synchronization. The source address is set to the location of the video framer peripheral, and the destination address is set to the start of the data buffer. Because the input address is static, the EDMA_TPCC_BDIX_n[15:0] SBIDX is 0 (no modification to the source address). The destination is made up of arrays of contiguous, linear elements; therefore, the EDMA_TPCC_BIDX_n[31:16] DBIDX is set to pixel size, 2 bytes. EDMA_TPCC_ABCNT_n[15:0] ANCT is equal to the pixel size, 2 bytes. EDMA_TPCC_ABCNT_n[31:16] BCNT is set to the number of pixels in an array, 640. EDMA_TPCC_CCNT_n[15:0] CCNT is equal to the total number of arrays in the block, 480. EDMA_TPCC_CIDX_n[15:0] SCIDX is 0 because the source address undergoes no increment. The EDMA_TPCC_CIDX_n[31:16] DCIDX is equal to the difference between the starting addresses of each array. Because one pixel is 16 bits (2 bytes), EDMA_TPCC_CIDX_n[31:16] DCIDX is equal to 640 × 2.
Figure 16-41 shows Bursting Peripherals Transfer.
(a) EDMA Parameters |
Parameter Contents | Parameter | |||||
0010 0004h | Channel Options Parameter (OPT) | |||||
Channel Source Address | Channel Source Address (SRC) | |||||
0280h | 0002h | Count for 2nd Dimension (BCNT) | Count for 1st Dimension (ACNT) | |||
Channel Destination Address | Channel Destination Address (DST) | |||||
0002h | 0000h | Destination BCNT Index (DSTBIDX) | Source BCNT Index (SRCBIDX) | |||
0000h | FFFFh | BCNT Reload (BCNTRLD) | Link Address (LINK) | |||
0500h | 0000h | Destination CCNT Index (DSTCIDX) | Source CCNT Index (SRCCIDX) | |||
0000h | 01E0h | Reserved | Count for 3rd Dimension (CCNT) |
(b) Channel Options Parameter (OPT) Content