EE345L Spring 2000 Quiz2 Page 1 of 4Jonathan W. Valvano First:_________________ Last:_____________________April 5, 2000, 11:00am-11:50amThis is an open book, open notes exam. You must put your answers on these pages only, you can use theback. You have 50 minutes, so please allocate your time accordingly. Please read the entire quiz before starting.(20) Question 1. For each situation, choose the best interface protocol to implement a serial channel. In particular,for each part simply write in your selection from the available choices (i.e., digital, RS232, RS422, or RS485). Youmay use the same protocol more than once, or not at all.TxDataSCIGroundA'B'RxDataSP301ABRS422TxDataSCIGroundRxData DigitalTxDataSCIGroundRxDRxDataSP232TxDRS232TxDataSCIGroundRxDataSP483ABRS485DEREDRBaud rate Distance Duplex Noise Your choice9600 30 ft half duplex very high9600 30 ft full duplex very high9600 3000 ft full duplex low500,000 30 ft full duplex medium500,000 3 in full duplex lowEE345L Spring 2000 Quiz2 Page 2 of 4(20) Question 2. The overall objective of this problem is to convert this gadfly SCI example to generate and receiveeven parity frames. Redesign the system so that even parity is generated on each 11-bit transmit frame that is output(1 start, 8 data, even parity, and 1 stop). You should also check for parity errors on each 11-bit receive frame that isinput. There is a protected global variable, which you will initialize to zero, and increment on every input frame thatis received in error.unsigned short ParErr; // number of parity errors detected by InChar()The following are the ritual, input, and output functions from SCI12.C. Please make the necessary changes.void InitSCI(void){ SC0BDH=0; SC0BDL=13; SC0CR1=0; SC0CR2=0x0C; };char InChar(void){ while ((SC0SR1 & RDRF) == 0){}; return(SC0DRL);}void OutChar(char data){ while ((SC0SR1 & TDRE) == 0){}; SC0DRL = data; if(data==CR){ /* if CR add LF */ while((SC0SR1 & TDRE) == 0){}; SC0DRL = LF;} else if(data==LF){ /* if LF add CR */ while((SC0SR1 & TDRE) == 0); SC0DRL = CR;}}EE345L Spring 2000 Quiz2 Page 3 of 4(60) Question 3. The overall objective of this problem is to record songs, which a musician plays on an 8-keypiano. The keys are labeled 0 through 7. Each of the 8 piano keys is a simple switch, which is closed (0Ω) whenthe key is touched, and is open when the key is released. There is 100 µs of bounce. You will design the hardwareinterface to the piano and write the song-recording software. The main program, which you do not write, will callyour ritual then perform unrelated operations. I.e., the song recording will occur in the background using interruptsynchronization. Time will be expressed as a 16-bit unsigned decimal fixed-point number, with a resolution of 0.01seconds. Time will vary from 0 to 655.35 seconds. Your system will measure the time when a key is pressed, andwhen it is released. The data structure used to store the song is as follows:struct Event{unsigned char KeyCode; // key number, 0 through 7unsigned char What; // 0 means touch, 1 means releaseunsigned short When;} // Time in 0.01 sec unitstypedef struct Event EventType;EventType Song[200]; // a song consists of up to 200 eventsIf the musician touches keys 1,3,5 at time 1.2345 sec, and releases them all at 9.8765 sec, the six entries would beSong[0]={1,0,124} means key 1 is touched at 1.24 secSong[1]={3,0,124} means key 3 is touched at 1.24 secSong[2]={5,0,124} means key 5 is touched at 1.24 secSong[3]={1,1,987} means key 1 is released at 9.88 secSong[4]={3,1,987} means key 3 is released at 9.88 secSong[5]={5,1,987} means key 5 is released at 9.88 sec(10) Part a) All eight keys will be interfaced to a single I/O port. Which port would you use? Justify?(10) Part b) Show the hardware interface between the piano and the 6812. Since each of the piano keys, numbered 0to 7, is separate and identical, you need only show the connection between Key0 and bit 0 of the port you selectedin part a. Decide whether to debounce in hardware or software. Select the best approach (direct, scanned, ormultiplexed.)6812I/O pin 0Key0(5) Part c) Show any additional global data structures required.EE345L Spring 2000 Quiz2 Page 4 of 4(15) Part d) Show the ritual that initializes the I/O port and data structures. You are free to use any of the availableinterrupt mechanisms. Arm and enable interrupts.(15) Part e) Show the ISR(s), which record the song. Stop recording (disarm) after 200 events are recorded or after655.35 seconds, whichever occurs first.(5) Part f) Show the C code that establishes the necessary interrupt