Schedule for the Remaining Presentations(EI 502)


24 Oct: 8251, 8257 and 8279
29 Oct: 8257 (2nd Group), 8253(2nd Group)
30 Oct: ADC and DAC

Answers to Quiz of 11 Sep 2011

Here are the answers to the questions of yesterday's quiz.

1.       Why should the data bus be bi-directional? 

      The data bus is used to send and receive data between various units such as the processor, memory, other peripherals etc. Thus, the bus has to be bi-directional.      

          

       What are the functions of the address bus?

       The function of an address bus is to transmit the binary address values to all the devices connected to it. The memory and I/O devices then would be able to detect if there is a request fro data from them. The specific address on the bus will tell the devices if the request is addressed to it. (if the address requested falls in its range of addresses)

      What are the control signals used in the control bus of a 8085 microprocessor?

      There are three control signals on the control bus of 8085A. These are the read (RD\), write(WR\) and the Interrupt acknowledge(INTA\) signals.

     

       Define Fetch, Decode, Execute phases of an instruction.

      Fetch is the first phase of the instruction cycle. The value available in PC is used to address memory. Content of the memory at that address is brought into the instruction register. This is the fetch phase. Depending on if the instruction is a multi-byte one, there may be more fetch cycle before execution can start.  

      How would you define a byte, nibble, and a word?

     

      A byte is 8 bits, a nibble is 4 bits and word is 16 bits( could be more in some computers).

      Describe the sequence of operations that take place when a microprocessor is powered on?

      The microprocessor is reset. A reset out signal goes out to all other blocks in the system to reset them (get them into a known starting phase). The instruction pointer/program counter is set to an initial value (most often 0000H). The microprocessor starts an op code fetch to this initial address. Content of this location is brought in, IP/PC is incremented, instruction is decoded and executed, another opcode fetch is initiated. This cycle continues unless a HLT instruction is executed or an illegal instruction is executed. In case of an illegal instruction the system will hang.

      What are the functions fulfilled by an accumulator?

      It holds variables, results of intermediate calculations.

       

      What do you understand by a flag inside a microprocessor?

      Flags are single bit hardware memory (flip-flops) that store the various status of last calculation done by the ALU. For example Z-zero, C-carry, P-parity, etc. could some flags used. Please note, different microprocessors may have a different set of flags.

      The program counter and the stack pointer inside 8085 are 16 bit in length. Why so?

      The program counter and the stack pointer are required to hold an address value which can be anywhere in the given memory space of the microprocessor. 8085 memory space is addressed by 16 bit values and hence these two registers must be 16 bit wide. 

  

      How could the various operations happening inside the 8085 MPU be identified?

      There are three status signals in 8085 that indicate the kind of machine cycle operation happening inside the microprocessors. These signals are IO/M\, S1 and S0 and the control signals. Thus they are able to indicate up to eight different types of machine cycles happening inside. Some of the possible cycles are the op code fetch, memory read, memory write, I/O read, I/O write, Interrupt Ack etc.

Special Note: Those who took this test on 10 Sep, please note that the questions 1,2,3, 4 ,5,7 and 8 are 1 mark each, questions 6 and 10 are 3 marks each and question 9 is for 2 marks for a total of 15 marks.

[EI 502, IC 503, EI 405, EI 611] My Microprocessor Design Book is finally Ready!

My last blog post was about a series of questions. If you, seriously, wanted to solve those problems you could do well by reading this text I had published quite a while back. I finally have a electronic version that can be shared easily. Send me  a mail at ddas15847@gmail.com  and I will share it with you. I need to update the book a bit and orient it with the WBUT syllabus. This version, as is, has a lot of solved problems and a lot of exercises too. If you would like a copy of the Electronic version, I'll give you a discount of the price on the forthcoming revised version.(It's free for my current EI 502 students, of course!) The current Electronic version will cost you Rs.150 and when the revised version comes out you would be able to buy that at list price minus Rs.150. If you are paying in USD it is $3.99.

[EI 502] Some questions on topics covered up to 31 Jul 2011

Here are some questions from items covered so far. Please try to answer them. We shall discuss the answers in a later post.

1.    What are the operations performed by a microprocessor?
2.    Why should the data bus be bi-directional?
3.    What are the functions of the address bus?
4.    What are the control signals used in the control bus of a 8085 microprocessor?
5.    Define Fetch, Decode, Execute phases of an instruction.
6.    How would you define a byte, nibble, word and a long word?
7.    What are the differences in a microprocessor based system and a hardware system?
8.    What are the functions of control unit in a microprocessor?
9.    Describe the sequence of operations that take place when a microprocessor is powered on?
10.  What are tri-state devices?
11. What are buffers?
12.  Explain the workings of a latch.
13.  What are the functions fulfilled by an accumulator?
14. What do you understand by a flag inside a microprocessor?
15.  The program counter and the stack pointer inside 8085 are 16 bit in length. Why so?
16. What starts to happen when a 8085 microprocessor?
17. How could the various operations happening inside the 8085 MPU be identified?
18. Why are tri-state devices required in a microprocessor based system?

[EI 502] Some Preliminary Information on Microprocessors

Here are some references you will find useful.

• Without the 4004 the PC Revolution Would Not Have Happened, 
• Computer Revolution Would not Have Happened Without the 4004
• Intel 8088 That Started the PC Revolution

[IT802D] Answers to Class Test1 Questions

Following are the correct answers to the questions of the 1st class test. The answers are in blue.

1. Answer the following (5 x 1)
1. What is the frequency band used by a mobile handset? (Depending on the country and the generation of the system, it 900, 12800 or 1900 MHz bands)
2. What is the main difference in the way GSM and CDMA mobile phones communicate? (In GSM several cells are set up and a base station in each cell communicates with the mobile stations. Whereas CDMA does not need that and covers all its users in a region through one access.)
3. What services are provided through GPRS?(Mainly the Internet access)
4. What is the earliest system of mobile communication?(NMT systems in Europe are the oldest, AMPS is the oldest in US)
5. What is the standard for wireless LAN? (The standard governing wireless LAN is the 802.11x family)
2. Answer the following (2 + 3)
1. Describe the advantages of mobile phones over landline phones.( You can communicate even when moving. That is the biggest advantage of the system.Users do not need to be in a fixed location to receive or make calls)
2. What is a cell in cellphone communication, explain with a sketch?(A cell in the cellular system is the area served by one base station. Conceptually they are hezagonal. But, that is only a convenience of representation. With a hexagonal shape you could represent coverage without gaps.)
3. Describe in couple of lines various modulation schemes (max of 5). (5)( Look up the details in the book. Some example schemes could be the Amplitude shift keying, phase shift keying, frequency shift keying, QAM, QPSK etc.)

     

Sets of slides- IT 802D course

The introductory as well as details about GSM systems have been posted at the slideshare site. Find all the presentations here. If there are any questions about these please do send me a mail at ddas15847@gmail.com or ask them here as comments.

[IT 802D] Near Field Communication (NFC)

In the last few days, I came across this term quite a few times. the concept seems interesting. Google is already deploying the technology. In a typical arrangement, business will have these NFC stickers and users with mobile devices, like the smartphone, can place a device very near these stickers and read off a lot of details.Business can tell them all about their business, much in the fashion of a home page on a site.

As use of wireless is proliferating, this technology should not interfere with any other wireless stuff. Hence these will use extreme low power such that the transmission is usable only in a few inches area of it.

[IT 802D] Mobile Communications-It's Really Interesting Right Now!!!!

Wireless communications for mobile devices is a big thing right now. Tablets are here and is a phenomenon, eReaders is a big deal too. Recently opened CES is reporting there are at least 100 different tablets being presented this year. Blutooth has been around for quite a while now. Wi-Fi, WiMAX and what have you! People want everything to be turn into wonders without wires. Then there is that NFC thing or the near field communications, a few inches! Could not have been a more appropriate time to read about mobile communications!