Solution for Question 9 : IES Conventional 1998 : Electronics & Telecommunication Engineering : Paper II

Q.9. (a): Explain with the help of D flip-flops, SR flip-flops and logic gates the working of all Interrupts available in the Microprocessor 8085 CPU. 

Solution: INTR, RST 5.5, RST 6.5 and RST 7.5 are enabled only if interrupt enable flip has high EI signal at its input. The interrupt enable flip flop gets disabled if any of signals like DI (disable interrupts), Reset and any interrupt recognized are fed to OR gate connected at the input R of flip flop.

     RST 5.5, RST 6.5 and RST 7.5 has additional control through mask input fed to AND gates. When signal on mask is low then RST 5.5, RST 6.5 and RST 7.5 are enabled. RST 7.5 has additional control through D flip flop. The RST 7.5 is enabled only when both reset and RST 7.5 interrupt recognized signals are low. RST 7.5 is edge triggered as request can be stored in D flip flop.

     TRAP is non maskable interrupt which cannot be disabled by interrupt enable flip flop as shown in figure. It is level as well as edge triggered. It cannot be acknowledged again until it makes a transition from high to low to high. When TRAP interrupt is given to processor the service routine stored at 0024H is called immediattely.

     RST 5.5, RST 6.5 and INTR are level triggered. The signal should be kept high until microprocessor completes the execution of current instruction. 

Service routine of RST 5.5 is stored at 002CH, that of RST 6.5 at 0034H and RST 7.5 has its service routine at 003CH.

Q.9. (b): Derive the major differences between the HDTV System and the NTSC System.

Solution: 

NTSC and PAL resolutions

NTSC (National Television System Committee) resolution is analog video standards. It is relevant to network video since video encoder provide such resolutions when they digitize signals from analog cameras. Current PTZ network cameras and PTZ dome network cameras also provide NTSC resolutions since such cameras today use a camera block (which incorporates the camera, zoom, auto-focus and auto-iris functions) made for analog video cameras, in conjunction with a built-in video encoder board.

In North America and Japan, the NTSC standard is the predominant analog video standard, while in Europe and many Asian and African countries, the PAL standard is used. Both standards originate from the television industry. NTSC has a resolution of 480 lines and uses a refresh rate of 60 interlaced fields per second (or 30 full frames per second). A new naming convention, which defines the number of lines, type of scan and refresh rate, for this standard is 480i60 (“i” stands for interlaced scanning). 

High-definition television (HDTV)

HDTV provides up to five times higher resolution than standard analog TV. HDTV also has better color fidelity and a 16:9 format. Defined by SMPTE (Society of Motion Picture and Television Engineers), the two most important HDTV standards are SMPTE 296M and SMPTE 274M.

• SMPTE 296M (HDTV 720P) defines a resolution of 1280x720 pixels with high color fidelity in a 16:9 format using progressive scanning at 25/30 Hertz (Hz), which corresponds to 25 or 30 frames per second depending on the country, and at 50/60 Hz (50/60 frames per second).
• SMPTE 274M (HDTV 1080) defines a resolution of 1920x1080 pixels with high color fidelity in a 16:9 format using either interlaced or progressive scanning at 25/30 Hz and 50/60Hz.

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