SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
In order to save a device pin, there is a case where a skew may be inserted into VSYNC (with respect to HSYNC) when HSYNC is used as a start of line indicator as described in Figure 11-33. In this case, no FIELD ID signal is sent by the source chip. A description of Field ID determination by VSYNC skew is shown in Figure 11-38.
The active polarity of VSYNC falling within n pixel clock cycles of the first active cycle of HSYNC indicates the field id. If VSYNC is active before this time window, then the FIELD_ID = ‘1’ for the next picture. If VSYNC becomes active within this window, then FIELD_ID = ‘0’ for the next picture.
When using FID determination by VSYNC skew, the value for VSYNC is also determined by transitions in the window as shown in Figure 11-35.
The VIP_PARSER supports a configuration FID_POLARITY bit within VIP_PORT_A and VIP_PORT_B registers. For FID determination by VSYNC Skew, the fid determination functions are described in Table 11-9.
FID_POLARITY | Transition in Pre/Post Range | FID Determination |
---|---|---|
0 | No | 1 |
0 | Yes | 0 |
1 | No | 0 |
1 | Yes | 1 |