AXI VDMA operations begin with the setup of the video parameter and start address registers and the VDMA control registers. The following lists the minimum steps, in order, required to start AXI VDMA operations:
1.Write control information to the channel VDMACR register (Offset 0x00 for MM2S and 0x30 for S2MM) to set interrupt enables if desired, and set VDMACR.RS=1 to start the AXI VDMA channel running.
2.Write a valid video frame buffer start address to the channel START_ADDRESS register 1 to N where N equals Frame Buffers (Offset 0x5C up to 0x98 for MM2S and 0xAC up to 0xE8 for S2MM). Set the REG_INDEX register if required.
When AXI VDMA is configured for an address space greater than 32, each start address is to be programmed as a combination of two registers where the first register is used to specify LSB 32 bits of address while the next register is used to specify MSB 32 bits.
3.Write a valid Frame Delay (valid only for Genlock Slave) and Stride to the channel FRMDLY_STRIDE register (Offset 0x58 for MM2S and 0xA8 for S2MM).
4.Write a valid Horizontal Size to the channel HSIZE register (Offset 0x54 for MM2S and 0xA4 for S2MM).
5.Write a valid Vertical Size to the channel VSIZE register (Offset 0x50 for MM2S and 0xA0 for S2MM). This starts the channel transferring video data.
You should be able to update video parameter settings at any time while the engine is running by writing new video parameters and a video start address through the AXI4-Lite control interface. The newly written video transfer values take effect on the next frame boundary after you write the vertical size register for the respective channel.
To update video parameters dynamically while AXI VDMA operations are ongoing, a similar process to the start steps is needed.
1.Write the Frame Delay, Stride, and Horizontal Size in any order for the associated channel.
2.Write the Vertical Size. When VSize is written, the video register values are transferred to an internal register block. On the next frame boundary the VDMA controller for the associated channel starts transfers using the newly updated values.