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// SPDX-License-Identifier: Apache-2.0
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 = ShiftRegisters(in, n, en).lastOption.getOrElse(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 =
ShiftRegisters(in, n, resetData, en).lastOption.getOrElse(in)
}
object ShiftRegisters {
/** Returns a sequence of delayed input signal registers from 1 to n.
*
* @param in input to delay
* @param n number of cycles to delay
* @param en enable the shift
*/
def apply[T <: Data](in: T, n: Int, en: Bool = true.B): Seq[T] =
Seq.iterate(in, n + 1)(util.RegEnable(_, en)).drop(1)
/** Returns delayed input signal registers with reset initialization from 1 to n.
*
* @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
*/
def apply[T <: Data](in: T, n: Int, resetData: T, en: Bool): Seq[T] =
Seq.iterate(in, n + 1)(util.RegEnable(_, resetData, en)).drop(1)
}
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