EE 308 Spring 2012EE 308 – Homework 5Due Feb. 22, 2012For the homework problems which follow assume you have included the file derivative.h in yourC program. Thus, you can refer to PORTB when you want to access a byte at address 0x0001.Where I ask for ”some code” just write that part of a C program which will do the task. WhereI ask for ”a program” write a complete program, include the #include "derivative.h" line, thedeclaration of variables, the main() function, etc.1. Write some C code which will clear bits 4 and 2 and s et bits 3 and 5 of the eight-bit registerat address 0x0048 while leaving the other bits unchanged.2. Write some C code which will set bits 12, 10, 5 and 1 of the sixteen-bit register at address0x0076 while leaving the other bits unchanged.3. Write some C code which will set bit 0 of PORTB if the 16-bit value at address 0x0044 is lessthan 0x4000, and will clear bit 0 of PORTB if the value is greater than or equal to 0x4000.Treat the 16-bit number at 0x0044 as unsigned.4. Write some C code which will wait until Bit 8 of the eight-bit number at address 0x004dbecomes clear.5. Write a C program which will find the largest and smallest 8-bit number in memory locations0x8000 to 0x80ff. Store the maximum in address 0x1000 and the minimum in address 0x1002.Treat the numbers as unsigned.6. An MC9S12 has the following in some of its registers:TSCR1 TSCR2 TFLG20x80 0x03 0x80(a) Is the timer subsystem enabled? How can you tell this?(b) How long will it take (in ms) for the timer to overflow? How can you tell this?(c) Has the timer overflowed since the last time the TOF flip-flop was reset? How can youtell this?7. Write a C function which does the following: the function will be called with one eight-bitargument, and will return one eight-bit value. Write the argument to PORTB, then incrementits value and return that new value.8. Write a C function which does the following: the function will be called with one argumentand will return one eight-bit value. Write the argument to PORTB, then generate the nextpattern in the sequence for an eight-bit Johnson counter. The procedure to do this is asfollows: Shift the prese nt pattern to the right by one bit. The most significant bit of the nextpattern is the inverse of the least significant bit of the present pattern. The function returnthe eight-bit value of the next pattern.1EE 308 Spring 20129. Write a C function to take the next entry out of a table, write it to PORTB, and update theindex into the table. Here is an example of what the table might look like:const char table[] = {0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};The function is called with one argument, which is the index of the pattern to write toPORTB. Your co de should write the table entry corresponding to the index to PORTB. (Forexample, if table_index were 5, you would write the fifth e leme nt of the table, 0x10, toPORTB.) The function should return the index of the next element of the table. Make surethat index stays between 0 and the end of the table.10. Write a C function to generate the next sequence in the pattern shown below. You shouldhave two static variables in the function, one which starts with the value 0x80 and the otherwhich s tarts with the value 0x01. OR the two variables together to get 0x81, the first patternin the sequence. Then shift the first variable to the right by one (to get 0x40), and shiftthe second variable to the left by one (to get 0x02). ORing these two together to get 0x42,the se cond pattern in the sequence. Continue shifting the first variable to the right and thesecond to the left, and ORing the two together. When the result of the OR is 0x00, reset thepattern to the first in the sequence.11. Write a C program for Part 1 of Lab 3. The program will display four different patterns onthe LED display connected to Port B. You will use the state of bits 1 and 0 of the onboardDIP switch to select which of the four patterns to display. Write a program to set up PortB as an eight bit output port (be sure to disable the seven-segment displays, and to enablethe individual LEDs), and to implement (i) a binary up counter, (ii) a shifting bit, (iii) aJohnson counter, and (iv) a Ford Thunderbird style turn signal based on the state of theDIP switches. (These are the four subroutines from Problems 6 to 9.) Insert a 100 ms delaybetween updates of the display. Write the delay as a subroutine. Be sure to initialize thestack pointer in you program.Use four variables to hold information on the four patterns. Initialize these four variables tothe first pattern in the sequence.You should have a loop which checks the DIP switches connected to Port H. If bit 7 of theDIP switches is high, end the loop and exit back to DBug-12 with a SWI instruction. If bit 7of the DIP switches is low, check bits 0 and 1 to determine what pattern to display:PH1 PH0 Pattern0 0 Binary Up Counter0 1 Crossing Pattern1 0 Johnson Counter1 1 TBird Turn SignalFor example, if bits 1 and 0 of Port H are 10, call the Johnson Counter function with theJohnson Counter variable as its argument, and save the returned value into the JohnsonCounter variable. Call the Delay subroutine, then loop back to check the DIP switches
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