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// 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)
}
}
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