Intel Microprocessor Interview Questions and Answers
Briefly explain the 8279 operation.
The 8279 is basically a programmable keyboard and a component for display interfacing.
The 8279 can scan and also encode a 64 key keyboard as well as a numerical display of 16 digits.
The keyboard has a buffer based on FIFO to store up to 8 keys after which the processor must retrieve a character.
It contains 8 lines that can be used to connect to 8 columns of a keyboard. There are two additional lines for STB keys.
Once a key is pressed they are automatically debounced and it can function using two modes -key lockout and n-key roller.
On simultaneous presses only the first key is detected. In case of n-key rollover mode all simultaneous presses are detected and stored in the internal buffer.
Describe briefly any three types of transmission?
The various types of commonly used transmissions are as follows:
Simplex Transmission: This type of data transmission involves data to be moved only in one direction. In this no data can be sent back using the same channel. A
good example of this form of transmission can be found in a keyboard.
Half Duplex Transmission: This type of transmission allows data to be transferred in both directions but not at the same time. One end transmits while the other
Full Duplex Transmission: In this type of transmission data can be sent and received at the same time. There are no two different modes such as transmit and
Briefly mention the differences between VGA and CGA graphics.
The characteristics of CGA are as follows:
The CGA or the Color/Graphics adapter was the first color graphics card for IBM pc`s.
It contain 16KB of video memory and used an Rca jack to connect to a Tv or monitor ( NTSC compatible).
It could also be connected to a RBGI interface CRT monitor (4-bit).
The characteristics of VGA graphics are as follows:
The VGA or the video graphics array was a hardware introduced with the IMB PS/2 computers.
It has been widely adopted world over and now actually implies the analog computer display standard.
Eventually after much modifications by other manufacturers the VGA was superseded by SVGA.
What do you understand by VESA local bus? Mention the cons of using it?
VESA stands for Video Electronics Standards Association. It is used for the transmission of high speed input-output operations as well as to directly access the
It comprises of a various videos card and monitor manufacturers , they creates standards to define the resolution, number of colors, and other display properties.
In this way graphics cards have direct access to the processor and system memory. It does not suffer from limitations of the ISA bus.
Some of the cons of using VESA are as follows:
VESA suffers from interoperability issues.
VESA Standard is also unreliable as there are multiple cases in which the hardware such as the monitor or the card to display are unstable and buggy.
Highly dependent on the hardware configuration, getting the right combination is generally difficult.
VLB cards are not easy to install / service.
Describe briefly the external and internal bus of the 8088 processor.
Internal Data Bus: As its name suggests the internal data bus only works inside a CPU that is internally. It is able to communicate with the internal cache memories of
the CPU. Since they are internally placed they are relatively quick and are now affected by the rest of the computer.
External Data bus: This type of bus is used to connect and interface the computer to its connected peripheral devices. Since they are external and do not lie within the
circuitry of the cpu they are relatively slower.
The 8088 processor in itself contains a 16-bit internal data bus coupled with a 20-bit address register. This allows the processor to address to a maximum of 1 MB