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// SPDX-License-Identifier: Apache-2.0
package cookbook
import chisel3._
import chisel3.util._
/* ### How do I create a finite state machine?
*
* Use ChiselEnum to construct the states and switch & is to construct the FSM
* control logic
*/
class DetectTwoOnes extends Module {
val io = IO(new Bundle {
val in = Input(Bool())
val out = Output(Bool())
})
object State extends ChiselEnum {
val sNone, sOne1, sTwo1s = Value
}
val state = RegInit(State.sNone)
io.out := (state === State.sTwo1s)
switch(state) {
is(State.sNone) {
when(io.in) {
state := State.sOne1
}
}
is(State.sOne1) {
when(io.in) {
state := State.sTwo1s
}.otherwise {
state := State.sNone
}
}
is(State.sTwo1s) {
when(!io.in) {
state := State.sNone
}
}
}
}
class DetectTwoOnesTester extends CookbookTester(10) {
val dut = Module(new DetectTwoOnes)
// Inputs and expected results
val inputs: Vec[Bool] = VecInit(false.B, true.B, false.B, true.B, true.B, true.B, false.B, true.B, true.B, false.B)
val expected: Vec[Bool] =
VecInit(false.B, false.B, false.B, false.B, false.B, true.B, true.B, false.B, false.B, true.B)
dut.io.in := inputs(cycle)
assert(dut.io.out === expected(cycle))
}
class FSMSpec extends CookbookSpec {
"DetectTwoOnes" should "work" in {
assertTesterPasses { new DetectTwoOnesTester }
}
}
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