Problem 1: Synchronous circuit for a washing machine
1. Using the description of the design below, develop an ASMD
2. Complete a state diagram
The circuit has three external inputs, START, FULL, and EMPTY (which are 1 for at most of a single clock cycle and are mutually exclusive), and external output, HOT, COLD, DRAIN, and TURN. The datapath for the control consists of a down-counter, which has three inputs, RESET, DEC and LOAD. This counter synchronously decrements once each minute for DEC=1, but can be loaded or synchronously reset on any cycle clock CK. It has a single output, ZERO, which is 1 whenever the counter contains value zero and is 0 other wise.
In its operation, the circuit goes through four distinct cycles, WASH, SPIN, RINSE, and SPIN, which are detailed as follows.
WASH: Assume that the circuit is in its power-up state IDLE. If START is 1 for a clock cycle, HOT becomes 1 and remains 1 until FULL=1, filling the washer with hot water. Next, using LOAD, the down-counter is loaded with a value from a panel dial which indicates how many minutes the wash cycle is to last. DEC and TURN then become 1 and the washer washes its contents. When ZERO becomes 1, the wash is complete, and TURN and DEC becomes 0.
SPIN: Next, DRAIN becomes 1, draining the wash water. When EMPTY becomes 1, the down-counter is loaded with 7. DEC and TURN then become 1 and the remaining wash water is wrung from the contents. When ZERO becomes 1, DRAIN, DEC, and TURN return to 0.
RINSE: Next, COLD becomes 1 and remains 1 until FULL=1, filling the washer with cold rinse water. Next, using LOAD, the down-counter is loaded with the value 10. DEC and TURN then become 1 and the washer rinses its contents. When ZERO becomes 1, the rinse is complete, and TURN and DEC become 0.
SPIN: Next, DRAIN becomes 1, draining the rinse water. When EMPTY becomes 1, the down-counter is loaded with 8. DEC and TURN then become 1 and the remaining rinse water is wrung from the contents. When ZERO becomes 1, DRAIN, DEC, and TURN return to 0 and the circuit returns to state IDLE.