CS609 System Programming Assignment 2 Solution Fall 2013

Question 1:

Serial port contains a special chip for input/output which can communicate in two different modes. Explore and describe these modes and which one is better in the serial communication.

Note: Solutions containing the image of any text will reward zero marks.


UARTs (Universal Asynchronous Receiver Transmitter) are serial chips on your PC motherboard (or on an internal modem card)

There are two basic types of UARTs: dumb UARTS and FIFO UARTS

Read more:  http://www.tldp.org/HOWTO/Serial-HOWTO-18.html

Question 2:                                                                                                                               Marks 04     

Data is written at UART internal Transmitter Holding Register. What do you think is the role of Transmit Shift Register and TxD line during this write operation?


Transmit Shift Register is used for parallel to serial communication.
Data that comes from transmitter holding register parallel transmitted in Transmit Shift register and that register output it serially through TxD line. TxD is used to take transmitted data from Transmit Shift Register and use it in communication.

Question 3:                                                                                                                               Marks 06     

DTE wants to communicate with the DCE using RS232C Protocol. How does this communication start and end?  Identify the steps involved from the starting signal to ending signal between DTE and DCE device.


DTE stands for Data Terminal Equipment. A computer is a DTE. DCE stands for Data Communication Equipment. A modem is a DCE.
DTE normally comes with a Male Connector, while DCE comes with a Female Connector. However, that is not always true. Use the simple way below to confirm: Measure Pin 3 and Pin 5 of a DB-9 Connector with a Volt Meter, if you get a voltage of -3V to -15V, then it is a DTE device. If the voltage is on Pin 2, then it is a DCE device.
A straight-through cable is used to connect a DTE (e.g. computer) to a DCE (e.g. modem), all signals in one side connected to the corresponding signals in the other side in a one-to-one basis. A crossover (null-modem) cable is used to connect two DTE directly, without a modem in between. They cross transmit and receive data signals between the two sides and there are many variations on how the other control signals are wired: