The Video Timing Controller Inputs and Outputs are discussed and shown with timing diagrams in the following sections.
The blanking and active period definitions were discussed in Overview . In addition to these definitions, the period from the start of blanking (or end of active video) to the start of synchronization is called the front porch. The period from the end of synchronization to the end of blanking (or start of active video) is called the back porch. The total horizontal period (including blanking and active video) can also be defined, and similarly the total vertical period.
This Figure shows the start of the horizontal front porch (Hblank Start), synchronization (Hsync Start), back porch (Hsync End) and active video (SAV). It also shows the start of the vertical front porch (Vblank Start), synchronization (Vsync Start), back porch (Vsync End) and active video (SAV). The total number of horizontal clock cycles is HSIZE and the total number of lines is the VSIZE.
X-Ref Target - Figure 3-2
These definitions of video frame periods are used for both Video Timing Detection and Video Timing Generation .
IMPORTANT: Note that pixels-per-clock for video data and timing is non-existent in the Video Timing Controller. There is only a single set of timing signals for the video data bus. This means that horizontal timing settings can be detected and generated only for a multiple of the pixels-per-clock configured in the system. For example, given a video format where the active line is 1920, the system configured with a video data bus operating at 4 pixels-per-clock, the detected and generated timing for the active line would be (1920 pixels / 4 pixels-per-clock) = 480 clock (cycles). Similarly, all other horizontal components (i.e. hsync, hblank) would be effected, while the vertical components do not change.