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// See LICENSE for license details.
package chisel3.util
import chisel3._
object RegEnable {
/** Returns a register with the specified next, update enable gate, and no reset initialization.
*
* @example {{{
* val regWithEnable = RegEnable(nextVal, ena)
* }}}
*/
def apply[T <: Data](next: T, enable: Bool): T = {
val r = Reg(chiselTypeOf(next))
when (enable) { r := next }
r
}
/** Returns a register with the specified next, update enable gate, and reset initialization.
*
* @example {{{
* val regWithEnableAndReset = RegEnable(nextVal, 0.U, ena)
* }}}
*/
def apply[T <: Data](next: T, init: T, enable: Bool): T = {
val r = RegInit(init)
when (enable) { r := next }
r
}
}
object ShiftRegister
{
/** Returns the n-cycle delayed version of the input signal.
*
* @param in input to delay
* @param n number of cycles to delay
* @param en enable the shift
*
* @example {{{
* val regDelayTwo = ShiftRegister(nextVal, 2, ena)
* }}}
*/
def apply[T <: Data](in: T, n: Int, en: Bool = true.B): T = {
// The order of tests reflects the expected use cases.
if (n != 0) {
RegEnable(apply(in, n-1, en), en)
} else {
in
}
}
/** Returns the n-cycle delayed version of the input signal with reset initialization.
*
* @param in input to delay
* @param n number of cycles to delay
* @param resetData reset value for each register in the shift
* @param en enable the shift
*
* @example {{{
* val regDelayTwoReset = ShiftRegister(nextVal, 2, 0.U, ena)
* }}}
*/
def apply[T <: Data](in: T, n: Int, resetData: T, en: Bool): T = {
// The order of tests reflects the expected use cases.
if (n != 0) {
RegEnable(apply(in, n-1, resetData, en), resetData, en)
} else {
in
}
}
}
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