Embedded Microcomputer Systems
Exam 1 – Spring 2003
Do NOT write your name on this page. Write your name on the back of the last page of this exam.
Open book and open notes. Answer on these pages only, using the back of the page if necessary. Show
all of your calculations; don’t make me guess how you arrived at your answer. Read the entire exam
before proceeding.
1. (40) This Moore FSM controls traffic at an intersection. The 2-bit inputs and the 6-bit outputs are
given in binary. The wait times are given in seconds. The controller sequence is: output, wait, input, and
jump to next state, depending on the input. You are allowed to make minor modifications to the linked
structure, as long as the original FSM is implemented. Port C bits 1,0 are sensor inputs, and Port B bits 5-
0 are traffic light outputs.
goN
100001
30
waitN
100010
5
goE
001100
30
waitE
010100
5
00,01,10,11
01,11 00,01,
10,11 01,11
00,01
00,10
wait time
const struct State {
unsigned char Out; /* Output to Port B */
unsigned short Time; /* Time in sec to wait */
const struct State *Next[4]; /* Next if input=00,01,10,11 */
};
typedef const struct State StateType;
#define goN &fsm[0]
#define waitN &fsm[1]
#define goE &fsm[2]
#define waitE &fsm[3]
StateType fsm[4] = {
{0x21, 30, {goN,waitN,goN,waitN}}, /* goN state */
{0x22, 5, {goE,goE,goE,goE}}, /* waitN state */
{0x0C, 30, {goE,goE,waitE,waitE}}, /* goE state */
{0x14, 5, {goN,goN,goN,goN}} /* waitE state */
};
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