Merge branch 'master' into tobits-deprecation

1 files changed, 62 insertions, 0 deletions

diff --git a/src/main/scala/chisel3/util/Counter.scala b/src/main/scala/chisel3/util/Counter.scala
new file mode 100644
index 00000000..ba66d667
--- /dev/null
+++ b/src/main/scala/chisel3/util/Counter.scala
@@ -0,0 +1,62 @@
+// See LICENSE for license details.
+
+package chisel3.util
+
+import chisel3._
+//import chisel3.core.ExplicitCompileOptions.Strict
+
+/** A counter module
+ *
+  * @param n number of counts before the counter resets (or one more than the
+  * maximum output value of the counter), need not be a power of two
+  */
+class Counter(val n: Int) {
+  require(n >= 0)
+  val value = if (n > 1) Reg(init=UInt(0, log2Up(n))) else UInt(0)
+
+  /** Increment the counter, returning whether the counter currently is at the
+    * maximum and will wrap. The incremented value is registered and will be
+    * visible on the next cycle.
+    */
+  def inc(): Bool = {
+    if (n > 1) {
+      val wrap = value === UInt(n-1)
+      value := value + UInt(1)
+      if (!isPow2(n)) {
+        when (wrap) { value := UInt(0) }
+      }
+      wrap
+    } else {
+      Bool(true)
+    }
+  }
+}
+
+object Counter
+{
+  /** Instantiate a [[Counter! counter]] with the specified number of counts.
+    */
+  def apply(n: Int): Counter = new Counter(n)
+
+  /** Instantiate a [[Counter! counter]] with the specified number of counts and a gate.
+   *
+    * @param cond condition that controls whether the counter increments this cycle
+    * @param n number of counts before the counter resets
+    * @return tuple of the counter value and whether the counter will wrap (the value is at
+    * maximum and the condition is true).
+    *
+    * @example {{{
+    * val countOn = Bool(true) // increment counter every clock cycle
+    * val (counterValue, counterWrap) = Counter(countOn, 4)
+    * when (counterValue === UInt(3)) {
+    *   ...
+    * }
+    * }}}
+    */
+  def apply(cond: Bool, n: Int): (UInt, Bool) = {
+    val c = new Counter(n)
+    var wrap: Bool = null
+    when (cond) { wrap = c.inc() }
+    (c.value, cond && wrap)
+  }
+}