Programming the generation registers to the values shown in the following table results in the video timing signal outputs shown in the following figure.
In the following table, the Generator Encoding Register bits [3:0] are set to
0 to configure the number of lines skipped between each active
chroma line to be 0. This configures the Active Chroma output signal for 4:4:4 or 4:2:2
mode in which every line contains valid chroma samples.
| Register Address | Register Name | Value |
|---|---|---|
| 0x0060 | Generator Active Size | 0x0004_0003 |
| 0x0070 | Generator HSize | 0x0000_0007 |
| 0x0074 | Generator VSize | 0x0000_0008 |
| 0x0078 | Generator HSync | 0x0005_0004 |
| 0x0080 | Generator Frame 0 Vsync | 0x0006_0005 |
| 0x0068 | Generator Encoding | 0x0000_0000 |
| 0x006C | Generator Polarity | 0x0000_003F |
| 0x0000 | Control | 0x01FF_FF07 |
Figure 1. Generated Vertical Timing (4:4:4 Chroma)
The following C code shows how to configure the register values in the table using the VTC driver.
XVtc Vtc; /* Device driver instance */
XVtc_Signal SignalCfg; /* VTC Signal configuration */
XVtc_Polarity Polarity; /* Polarity configuration */
XVtc_SourceSelect SourceSelect;/* Source Selection configuration */
XVtc_Config *VtcCfgPtr;
VtcCfgPtr = XVtc_LookupConfig(VTC_DEVICE_ID);
XVtc_CfgInitialize(&Vtc, VtcCfgPtr, VtcCfgPtr->BaseAddress);
/* Setup the VTC Source Select config structure. */
/* 1=Generator registers are source */
/* 0=Detector registers are source */
memset((void *)&SourceSelect, 0, sizeof(SourceSelect));
SourceSelect.VBlankPolSrc = 1;
SourceSelect.VSyncPolSrc = 1;
SourceSelect.HBlankPolSrc = 1;
SourceSelect.HSyncPolSrc = 1;
SourceSelect.ActiveVideoPolSrc = 1;
SourceSelect.ActiveChromaPolSrc= 1;
SourceSelect.VChromaSrc = 1;
SourceSelect.VActiveSrc = 1;
SourceSelect.VBackPorchSrc = 1;
SourceSelect.VSyncSrc = 1;
SourceSelect.VFrontPorchSrc = 1;
SourceSelect.VTotalSrc = 1;
SourceSelect.HActiveSrc = 1;
SourceSelect.HBackPorchSrc = 1;
SourceSelect.HSyncSrc = 1;
SourceSelect.HFrontPorchSrc = 1;
SourceSelect.HTotalSrc = 1;
/* Setup the VTC Polarity config structure. */
memset((void *)&Polarity, 0, sizeof(Polarity));
Polarity.ActiveChromaPol = 1;
Polarity.ActiveVideoPol = 1;
Polarity.VBlankPol = 1;
Polarity.VSyncPol = 1;
Polarity.HBlankPol = 1;
Polarity.HSyncPol = 1;
/* Setup the VTC Signal config structure. */
memset((void *)&SignalCfg, 0, sizeof(XVtc_Signal));
SignalCfg.OriginMode = 1;//Set Frame Origin to Start of Active Video
SignalCfg.HTotal = 7;
SignalCfg.HActiveStart = 0;
SignalCfg.HFrontPorchStart = 3;// Active Video Width
SignalCfg.HSyncStart = 4;// Active Video Width + FP Width
SignalCfg.HBackPorchStart = 5;// Active Video Width + FP Width + Sync Width
SignalCfg.V0Total = 8;
SignalCfg.V0ChromaStart = 0;
SignalCfg.V0ActiveStart = 0;
SignalCfg.V0FrontPorchStart = 4;// Active Video Height
SignalCfg.V0SyncStart = 5;// Active Video Height + FP_Width
SignalCfg.V0BackPorchStart = 6;// Active Video Height + FP Width + Sync Width
/* Write VTC config to HW */
XVtc_RegUpdate(&VTC);
XVtc_SetPolarity(&Vtc, &Polarity);
XVtc_SetGenerator(&Vtc, &SignalCfg);
XVtc_SetSource(&Vtc, &SourceSelect);
/* Enable VTC Generator */
XVtc_Enable Generator(&Vtc);