DS730 Datasheet, PDF (34/46 Pages) Xilinx, Inc – LogiCORE IP Video Direct

LogiCORE IP Video Direct Memory Access v1.1
When writing a VFBC command, the Video DMA uses the VDMA Hsize to specify the horizontal length, the
VDMA Vsize to specify the vertical length, and the VDMA Stride to specify the stride between each line. There are
read and write versions of each of these registers that are used for read or write commands respectively. The Start
Address registers are used for the memory address in the VFBC command. The Video DMA sources the Start
Address registers in one of two ways based on the Circular Buffer Enable:
1. Circular Buffer Enable = 0: The address register index stored in “Frame Store Pointer” is used to specify that
Start Address register that is to be used for all transfers.
2. Circular Buffer Enable = 1: The core rotates though all of the valid Start Address registers. The valid Start
Address registers are determined by the “Frame Stores” parameter which specifies the number of Frame Stores
(also known as Start Address registers) to use. After reset, Start Address 0 is always the first register used in the
rotation. After each transfer, the core rotates to the next Start Address register. The core circles back to the Start
Address 0 once all of the valid Start Address registers have been accessed.
The trigger to begin a new transfer depends upon the “Use Frame Sync” option in the CORE Generator GUI. When
“Use Frame Sync” is selected, new transfers wait for the falling edge of the fsync signal. See the "Fsync
Synchronization" section for more details. When “Use Frame Sync” is not selected, new transfers wait for the
VFBC_Cmd_Idle signal to become active.
Figure 9 shows an example of a Free-Running Register Write transfer. Once vfbc_cmd_idle is active, the Video
DMA sends a write command to the VFBC and then begins the data transfer. A Free Running Register Read transfer
occurs in the same fashion.
X-Ref Target - Figure 9
Figure 9: Free-Running Register Write Command Mode
DS730 September 21, 2010
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Product Specification