TV Frame Buffer:
1) RAM could save two static images: A & B.
2) Subsystem could display image A or B on TV by getting the digital commands from the Remote Controller.
Video Sync Separator (LM1881 x 1)
Using separator to generate composite sync and vertical sync. C.S can be used to choose one line, and V.S can be use to choose one image. (Figure 4.3, 4.4, 4.5, 4.6)
Analog to Digital (74HC148 x 1 & LM339 x 2)
Using two comparators and one encoder to transfer Video Input (Analog signal) to digital signal. And the digital signal will be three outputs (D0, D1, D2). (Figure 4.7, 4.8)
Digital to Analog (LM356N x 2)
Three outputs from ADC will go through the resistors, and then connect together as one input of DAC. Using two amplifiers to transfer digital signal to analog signal. Displaying the output of DAC on TV will meet the requirement 3.II, which is outputting the live NTSC from the input digitized and reconstructed through the ADC – DAC. Also this will meet part of the requirement 1 which is image with a minimum of 5 gray levels. (Figure 4.9, 4.10)
Analog Mux (CD4051B x1) & Digital Mux (74HC125 x 1)
- Using analog multiplexer can get the command from remote controller to display two types of signal on TV. First one will meet the requirement 3.I, which is outputting the live NTSC from the input without transformation or modification. Second one will meet the requirement 3.II, which is outputting the live NTSC from the input digitized and reconstructed through the ADC – DAC.
- Using the tri-state buffer can control the three inputs from ADC be on or off. By getting the command from remote controller can display two images, A or B, Which meet the requirement 3.III and 3.IV, displaying a static image on the TV of stored image A and B. (Figure 4.11, 4.12, 4.13, 4.14)
X, Y Counter & Skipping 21 lines (74HC74 x 2 & 74HC04 x 1& 74HC08 x 2& 74HC590 x 3 & 4 MHZ oscillator x 1& 74HC11 x 1& 74HC32 x 1)
The X, Y Counter will generate the address to be used on the RAM. And the frequency divider and clock will make sure to get 128 lines Which meet rest of the requirement 1, receiving a trigger pulse store a 128 x 128 pixel image. And the Skipping 21 lines will work for the quality of the TV output by skipping the first 21 noise lines. (Figure 4.15, 4.20, 4.21)
RAM (CY62256N x 1 & 74HC10 x 1)
Using NAND gate can control the RAM to write or output (WE/OE). RAM can get the digital input from the three outputs of the ADC. And the addressing pin A14 can control to save static image A or B. A14 can connect to ground or power which meet the requirement 2, storing up to two images at a time, A & B. (Figure 4.16, 4.17, 4.18, 4.19, 4.22, 4.23)
Changmeng Lin 