Pixclk
VSYNC
HSYNC
FID
Pixclk
VSYNC
ACTVID
FID
Pixclk
VSYNC
ACTVID
FID
Internal Modules
149
SPRUHI7A – December 2012 – Revised June 2016
Copyright © 2012–2016, Texas Instruments Incorporated
High-Definition Video Processing Subsystem (HDVPSS)
1.2.8.2.5.3 Signal Subsets—4 Pin VSYNC, ACTVID, and FID
A sending device may use only a subset of the signals described in
. The sending
device just needs to convey important signals required to capture the field or frame. It can be shown that
various selections of four pins can be used to satisfy all Type 1 conditions.
Three pins, VSYNC, ACTVID, and FID, plus a pixel clock can be used to support discrete sync. VSYNC
would bump the capture buffer. An inactive to active level of ACTVID specifies a line of data to capture.
FID determines the field ID polarity. The scenario in which the sending device wants the receiving end to
capture Vertical Ancillary Data using 4-pin signaling is shown in
Figure 1-95. 4-Pin Reduced ACTVID Signaling with Vertical Ancillary Data
describes the case using the 4-pin interface in which the sending device does not send
Vertical Ancillary Data.
Figure 1-96. 4-Pin Reduced ACTVID Signaling with No Vertical Ancillary Data
1.2.8.2.5.4 Signal Subsets—4 Pin VSYNC, HSYNC, and FID
In this style of Discrete Sync, as shown in
, four pins are used including the Pixel Clock.
HSYNC signals the beginning of the line. All data in the line is captured, including Horizontal Blanking
Data. In fact, this signaling mode is the only one that allows Horizontal Blanking Data to be captured.
Of course, by capturing the horizontal blanking pixels in the frame buffers, there is no way to be certain
exactly where the blanking ends and the active video starts. One would have to rely solely on video format
specs to find the active video inside the frame buffer.
Figure 1-97. 4-Pin Reduced HSYNC Signaling with Vertical Ancillary Data