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rocket-chip/src/main/scala/util/Timer.scala
Henry Cook 4c595d175c Refactor package hierarchy and remove legacy bus protocol implementations (#845)
* Refactors package hierarchy.

Additionally:
  - Removes legacy ground tests and configs
  - Removes legacy bus protocol implementations
  - Removes NTiles
  - Adds devices package
  - Adds more functions to util package
2017-07-07 10:48:16 -07:00

96 lines
2.6 KiB
Scala

// See LICENSE.SiFive for license details.
// See LICENSE.Berkeley for license details.
package freechips.rocketchip.util
import Chisel._
/** Timer with a statically-specified period.
* Can take multiple inflight start-stop events with ID
* Will continue to count down as long as at least one event is inflight
*/
class Timer(initCount: Int, maxInflight: Int) extends Module {
val io = new Bundle {
val start = Valid(UInt(width = log2Up(maxInflight))).flip
val stop = Valid(UInt(width = log2Up(maxInflight))).flip
val timeout = Valid(UInt(width = log2Up(maxInflight)))
}
val inflight = Reg(init = Vec.fill(maxInflight) { Bool(false) })
val countdown = Reg(UInt(width = log2Up(initCount)))
val active = inflight.reduce(_ || _)
when (active) { countdown := countdown - UInt(1) }
when (io.start.valid) {
inflight(io.start.bits) := Bool(true)
countdown := UInt(initCount - 1)
}
when (io.stop.valid) { inflight(io.stop.bits) := Bool(false) }
io.timeout.valid := countdown === UInt(0) && active
io.timeout.bits := PriorityEncoder(inflight)
assert(!io.stop.valid || inflight(io.stop.bits),
"Timer stop for transaction that's not inflight")
}
/** Simplified Timer with a statically-specified period.
* Can be stopped repeatedly, even when not active.
*/
class SimpleTimer(initCount: Int) extends Module {
val io = new Bundle {
val start = Bool(INPUT)
val stop = Bool(INPUT)
val timeout = Bool(OUTPUT)
}
val countdown = Reg(UInt(width = log2Up(initCount)))
val active = Reg(init = Bool(false))
when (active) { countdown := countdown - UInt(1) }
when (io.start) {
active := Bool(true)
countdown := UInt(initCount - 1)
}
when (io.stop) { active := Bool(false) }
io.timeout := countdown === UInt(0) && active
}
object SimpleTimer {
def apply(initCount: Int, start: Bool, stop: Bool): Bool = {
val timer = Module(new SimpleTimer(initCount))
timer.io.start := start
timer.io.stop := stop
timer.io.timeout
}
}
/** Timer with a dynamically-specified period. */
class DynamicTimer(w: Int) extends Module {
val io = new Bundle {
val start = Bool(INPUT)
val period = UInt(INPUT, w)
val stop = Bool(INPUT)
val timeout = Bool(OUTPUT)
}
val countdown = Reg(init = UInt(0, w))
val active = Reg(init = Bool(false))
when (io.start) {
countdown := io.period
active := Bool(true)
} .elsewhen (io.stop || countdown === UInt(0)) {
active := Bool(false)
} .elsewhen (active) {
countdown := countdown - UInt(1)
}
io.timeout := countdown === UInt(0) && active
}