xref: /XiangShan/src/main/scala/device/AXI4Keyboard.scala (revision c6d439803a044ea209139672b25e35fe8d7f4aa0)

/***************************************************************************************
* Copyright (c) 2020-2021 Institute of Computing Technology, Chinese Academy of Sciences
*
* XiangShan is licensed under Mulan PSL v2.
* You can use this software according to the terms and conditions of the Mulan PSL v2.
* You may obtain a copy of Mulan PSL v2 at:
*          http://license.coscl.org.cn/MulanPSL2
*
* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
*
* See the Mulan PSL v2 for more details.
***************************************************************************************/

package device

import chisel3._
import chisel3.util._
import chipsalliance.rocketchip.config.Parameters
import freechips.rocketchip.diplomacy.AddressSet
import utils._

class KeyboardIO extends Bundle {
  val ps2Clk = Input(Bool())
  val ps2Data = Input(Bool())
}

// this Module is not tested
class AXI4Keyboard
(
  address: Seq[AddressSet]
)(implicit p: Parameters)
  extends AXI4SlaveModule(address, executable = false, _extra = new KeyboardIO)
{
  override lazy val module = new AXI4SlaveModuleImp[KeyboardIO](this){
    val buf = Reg(UInt(10.W))
    val ps2ClkLatch = RegNext(io.extra.get.ps2Clk)
    val negedge = RegNext(ps2ClkLatch) && ~ps2ClkLatch
    when (negedge) { buf := Cat(io.extra.get.ps2Data, buf(9,1)) }

    val cnt = Counter(negedge, 10)
    val queue = Module(new Queue(UInt(8.W), 8))
    queue.io.enq.valid := cnt._2 && !buf(0) && io.extra.get.ps2Data && buf(9,1).xorR
    queue.io.enq.bits := buf(8,1)
    queue.io.deq.ready := in.r.ready

    in.r.bits.data := Mux(queue.io.deq.valid, queue.io.deq.bits, 0.U)
  }

}