Q = x nor Q
Q = y nor Q
a) Draw this logic circuit. Neatness counts! (0.5 points)
b) For all possible values of x and y, show all possible values of Q and Q. Arrange this as a truth table, but note that some row or rows will have more than one value for each output. (0.5 points)
| x | y | Q |
| 0
| 0
| 0 | 1
| 1 | 0
| 0 | 1 | 1 | 0
| 1 | 0 | 0 | 1
| 1 | 1 | 0 | 0
| |
c) Using the truth table you worked out above, which combinarion of x and y should be used to make this flipflop hold a value? (0.2 points)
Set x and y to zero.
d) How do you make this flipflop hold Q = 1? Your instructions should assume that x and y are initially as specified in part c and that they return to that condition at the end. (0.3 points)
Given that x and y are initially zero, set y to 1 and then back to zero.
CR, by rights, ought to return the display pointer dspptr (the X coordinate) to the first byte on the current line, without changing the Y coordinate, and LF ought to move the display pointer down one line without changing the X coordinate.
a) Give C-like pseudocode for getat() a routine you could add to the Hawk monitor that returns, in R3 and R3, the current X and Y coordinates. Feel free to write things like return (x,y) to indicate the return of two different integers. You can compute X and Y from dispptr. (0.5 points)
(int,int) getat() {
int xy = origin - dspptr;
int col = xy % (* pcolumns);
int line = xy / (* pcolumns);
return (col, line)
}
b) Give C-like pseudocode for a modified version of putchar(ch) that outputs the character if it was not a CR or LF, and that properly interprets CR and LF. Feel free to use x,y=getat() and setat(x,y) in your code. (1.0 points)
void putchar( char ch ) {
if (ch == CR) {
(col, line) = getat()
col = 0;
putat( col, line )
} else if (ch == LF) {
(col, line) = getat()
line = line + 1;
putat( col, line )
} else {
* dspptr = ch;
dspptr = dspptr + 1;
}
}