DS730 Datasheet, PDF (33/46 Pages) Xilinx, Inc – LogiCORE IP Video Direct

LogiCORE IP Video Direct Memory Access v1.1
When configured in "Read/Write" mode, the Video DMA operates very similarly to the way it does for both the
write operation shown in Figure 6 and the read operation shown in Figure 7. The only restriction is that only one
command can be written to the VFBC at a time. The vdma_rcmd_full, vdma_rcmd_almost_full,
vdma_wcmd_full, and vdma_wcmd_almost_full signals can be used to determine when it is safe to write a
command to the VFBC. Figure 8 demonstrates simultaneous read and write operations.
X-Ref Target - Figure 8
Figure 8: Command Interface, Read and Write Commands
Register Command Mode
The Video DMA can be configured to have between 1 and 16 read or write address registers. The number of address
registers is specified in the CORE Generator GUI by the “Frame Stores” parameter. When operated in “Register
Command Mode,” the Video DMA uses the addresses stored in these registers when writing commands to the
VFBC. Typically, each register corresponds to a frame buffer in the temporary frame storage. The address and frame
store size/stride registers are not double-buffered within the VDMA. Register values are only used at the start of
each frame, but care must still be taken to ensure that current values are not overwritten.
There are a number of controls that affect the operation of the core when run in Register Command Mode. These
controls are discussed in the sections that follow.
Free-Running
In Free-Running Register Command Mode, the Video DMA automatically initiates transfers based upon the control
settings. The core watches the vfbc_cmd_idle flag and waits until the VFBC is idle before writing a command to
the port. The core can operate in two modes determined by “Frame Count Enable:”
1. Frame Count Enable = 0: The Video DMA initiates frame transfers indefinitely.
2. Frame Count Enable = 1: The Video DMA initiates only a specified number of frame transfers. The frame limit
is set by the “Read Frame Count” for read operations or “Write Frame Count” for write operations.
DS730 September 21, 2010
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Product Specification