Chameleon-PIC Nurve Networks, Chameleon-PIC Datasheet - Page 53

• Manufacturer Part Number: Chameleon-PIC
• Description: MCU, MPU & DSP Development Tools PIC24 & PROPELLER DEV SYSTEM (SBC)
• Manufacturer: Nurve Networks

Specifications of Chameleon-PIC

• Processor To Be Evaluated: PIC24
• Data Bus Width: 16 bit
• Interface Type: USB, VGA, PS/2, I2C, ISP, SPI
• Operating Supply Voltage: 3.3 V, 5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

11.2.5.1 Frame Construction
Referring to Figure 11.7. This diagram represents the NTSC color “Super Frame”. The complete NTSC spec actually has
4 fields per super frame (if you want to follow the spec and interlace 100%). We aren’t going to follow the spec 100%, but
we are going to follow some of the more important parts of the spec, one such area is in the “vertical sync” and
“equalization pulses” area, please concentrate your attention on this area of Figure 11.7, for the description below.
A Frame is composed of 262.5 lines (non-interlaced), 262 will suffice. Of those 262 lines, many of them are invisible due
to overscan, and some must be used for the vertical retrace pulse. Therefore, a first attempt to generate a video signal
frame is the following algorithm:
// Step 1: Draw the top over scan
For line = 1 to 8
// Step 2: Draw the active region of the scan, 240 lines
For line = 1 to 240
// Step 3: Draw the bottom over scan
For line = 1 to 10
// Step 4: Generate a vertical sync pulse, basically apply 0V to the signal for
// the time duration of scanlines, note, no HSYNC pulse is sent, no serrations
Video = 0.0V
Delay(4-6 Scanlines)
If you add up the lines, you will get a total of 262 lines including active, inactive, and retrace or vertical sync. Now, due to
overscan, you probably won’t be able to see more than 200-220 of the active scan video lines, they will typically be
beyond view. Thus, most games systems don’t waste draw them, and simple increase the overscan regions. So a good
rule of thumb is that active video should be from 192-224 lines with equal amount of top and bottom overscan.
Begin
Generate the next black scanline
End
Begin
Generate the next scanline
End
Begin
Generate the next black scanline
End
Figure 11.7 – NTSC “Super Frame” video signal reference for NTSC frame construction.
© 2009 NURVE NETWORKS LLC “Exploring the Chameleon PIC 16-Bit”
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