SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
External ICs generally produce discrete sync interface signals seen in Figure 9-58.
VBLNKrepresents the vertical blanking interval. Generally, vertical blanking is at the top of a NTSC/PAL field. In certain standards, the last few lines of a field or frame are in vertical blanking in addition to the beginning few lines in the following field or frame.
VSYNC is the vertical sync indicator. VSYNC is active during a portion of the vertical blanking. For NTSC and PAL, since these standards define an odd number of lines for a field pair, VSYNC can be use in conjunction with HSYNC to determine FID polarity. Generally, VSYNC is defined to transition inactive to active sometime during vertical blanking. This signal then transitions to an inactive state before the end of vertical blanking. Certain standards define the line numbers where VSYNC transitions.
HBLNK is the horizontal blanking interval for each line. The horizontal blanking is the same number of pixels whether the line is in the active video region or in the vertical blanking region of the scan.
ACTVID is the region of a line that is active video. It is the inverse of the HBLNK signal. The number of pixels in the ACTVID region is the same for a line in vertical blanking as a line in active video. ACTVID(1) is a situation where the signal toggles in vertical blanking as well as active video. ACTVID(2) shows the signal toggling only in non-vertical blanking regions. Once ACTVID transitions active, it stays active for every PIXCLK until the end of the line.
HSYNC transitions from inactive to active for the first pixel of each line, which is a horizontal blanking pixel. HSYNC will transition to the inactive state before the end of the line. HSYNC is similar to HBLNK in that they both transition active on the same PIXCLK cycle. However, HBLNK transitions inactive at the end of the horizontal blanking period. HSYNC can transition inactive either before or after the horizontal blanking period.
Group 1 signals define the vertical separation between fields or frames. Group 2 signals define the separation between lines. One of the Group 1 signals can be tied to the VSYNC input. The ACTVID(1) and ACTVID(2) signals from Group 2 are tied to the ACTVID input. One of the other two Group 2 signals, HBLNK or HSYNC, can be tied to the HSYNC input.
VIP_PORT_A[15] USE_ACTVID_HSYNC_N for Port A and VIP_PORT_B[15] USE_ACTVID_HSYNC_N for Port B defines whether the line separation method uses the signal from the ACTVID or the HSYNC input of the VIP_PARSER module.
VIP_PORT_A[22] DISCRETE_BASIC_MODE for Port A VIP_PORT_B[22] DISCRETE_BASIC_MODE for Port B determines whether discrete sync works as described in Section 9.4.5.6 Input Data Interface or whether a “basic mode” input handler is invoked.
By choosing one signal from Group 1 and one signal from Group 2, there should be a way to capture the external data.
1. VIP_PARSER module defines three discrete sync control signals: ACTVID, HSYNC, and VSYNC.
2. In order to capture external data PIXCLK must never stop, for either horizontal or vertical blanking.