Add Debug Module (#49)

* Add Debug Module * [debug] Remove unit tests, update System Bus register addresses, parameterize nComponents * [debug] Update Debug ROM contents to match updated addresses
2016-06-01 16:33:34 -07:00 · 2016-06-01 16:33:34 -07:00 · 740a6073f6
commit 740a6073f6
parent e8408f0a8a
1 changed files with 962 additions and 0 deletions
--- a/uncore/src/main/scala/debug.scala
+++ b/uncore/src/main/scala/debug.scala
@ -0,0 +1,962 @@
+// See LICENSE for license details.
+
+package uncore
+
+import Chisel._
+
+import junctions._
+import cde.{Parameters, Config, Field}
+import Math.{ceil, max, min}
+
+// *****************************************
+// Constants which are interesting even
+// outside of this module
+// *****************************************
+
+object DbRegAddrs{
+
+  def DMCONTROL    = UInt(0x10)
+
+  def DMINFO       = UInt(0x11)
+  def AUTHDATA0    = UInt(0x12)
+  def AUTHDATA1    = UInt(0x13)
+  def SERDATA      = UInt(0x14)
+  def SERSTATUS    = UInt(0x15)
+  def SBUSADDRESS0 = UInt(0x16)
+  def SBUSADDRESS1 = UInt(0x17)
+  def SBDATA0      = UInt(0x18)
+  def SBDATA1      = UInt(0x19)
+  //1a
+  def HALTSUM      = UInt(0x1B)
+  //1c - 3b are the halt notification registers.
+  def SBADDRESS2    = UInt(0x3d)
+  // 3c
+  def SBDATA2       = UInt(0x3e)
+  def SBDATA3       = UInt(0x3f)
+}
+
+/** Constant values used by both Debug Bus Response & Request
+  */
+
+object DbBusConsts{
+
+  def dbDataSize = 34
+
+  def dbRamWordBits = 32
+
+  def dbOpSize = 2
+  def db_OP_NONE            = UInt("b00")
+  def db_OP_READ            = UInt("b01")
+  def db_OP_READ_WRITE      = UInt("b10")
+  def db_OP_READ_COND_WRITE = UInt("b11")
+
+  def dbRespSize = 2
+  def db_RESP_SUCCESS     = UInt("b00")
+  def db_RESP_FAILURE     = UInt("b01")
+  def db_RESP_HW_FAILURE  = UInt("b10")
+  // This is used outside this block
+  // to indicate 'busy'.
+  def db_RESP_RESERVED    = UInt("b11")
+
+}
+
+object DsbBusConsts {
+
+  def sbAddrWidth = 12
+  def sbIdWidth   = 10 
+
+  /* These are the default ROM contents, which support
+   * RV32 and RV64. RV128 are implemented as NOP.
+   * See the Debug Specification for the code.
+   */
+
+  def defaultRomContents : Array[Byte] = Array(0x6f, 0x00, 0x00, 0x06, 0x6f, 0x00, 0xc0, 0x00, 0x13, 0x04, 0xf0, 0xff,
+    0x6f, 0x00, 0x80, 0x00, 0x13, 0x04, 0x00, 0x00, 0xf3, 0x24, 0x40, 0xf1,
+    0x23, 0x20, 0x90, 0x10, 0x0f, 0x00, 0xf0, 0x0f, 0xf3, 0x24, 0x00, 0xf1,
+    0x63, 0xc6, 0x04, 0x00, 0x83, 0x24, 0xc0, 0x43, 0x6f, 0x00, 0xc0, 0x01,
+    0x93, 0x94, 0x14, 0x00, 0x63, 0xc6, 0x04, 0x00, 0x83, 0x34, 0x80, 0x43,
+    0x6f, 0x00, 0xc0, 0x00, 0x13, 0x00, 0x00, 0x00, 0x23, 0x2e, 0x80, 0x42,
+    0x73, 0x24, 0x00, 0x7b, 0x13, 0x74, 0x84, 0x00, 0x63, 0x04, 0x04, 0x00,
+    0x6f, 0x00, 0x80, 0x05, 0x73, 0x24, 0x20, 0x7b, 0x73, 0x00, 0x20, 0x7b,
+    0x73, 0x10, 0x24, 0x7b, 0x73, 0x24, 0x00, 0x7b, 0x13, 0x74, 0x04, 0x1c,
+    0x13, 0x04, 0xd4, 0xff, 0x63, 0x18, 0x04, 0x02, 0x0f, 0x10, 0x00, 0x00,
+    0x73, 0x24, 0x00, 0xf1, 0x63, 0x46, 0x04, 0x00, 0x23, 0x2e, 0x90, 0x42,
+    0x67, 0x00, 0x00, 0x40, 0x13, 0x14, 0x14, 0x00, 0x63, 0x46, 0x04, 0x00,
+    0x23, 0x3c, 0x90, 0x42, 0x67, 0x00, 0x00, 0x40, 0x13, 0x00, 0x00, 0x00,
+    0x67, 0x00, 0x00, 0x40, 0x73, 0x24, 0x40, 0xf1, 0x23, 0x26, 0x80, 0x10,
+    0x73, 0x60, 0x04, 0x7b, 0x73, 0x24, 0x00, 0x7b, 0x13, 0x74, 0x04, 0x02,
+    0xe3, 0x0c, 0x04, 0xfe, 0x6f, 0xf0, 0xdf, 0xfb).map(x => x.toByte)
+
+}
+
+
+
+object DsbRegAddrs{
+
+  def CLEARDEBINT  = UInt(0x100)
+  def SETHALTNOT   = UInt(0x10C)
+  def SERINFO      = UInt(0x110)
+  def SERBASE      = UInt(0x114)
+  // For each serial, there are
+  // 3 registers starting here:
+  // SERSEND0
+  // SERRECEIVE0
+  // SERSTATUS0
+  // ...
+  // SERSTATUS7
+  def SERTX_OFFSET   = UInt(0)
+  def SERRX_OFFSET   = UInt(4)
+  def SERSTAT_OFFSET = UInt(8)
+
+}
+
+
+// *****************************************
+// Configuration & Parameters for this Module
+// 
+// *****************************************
+
+/** Enumerations used both in the hardware
+  * and in the configuration specification.
+  */
+
+object DebugModuleAuthType extends scala.Enumeration {
+  type DebugModuleAuthType = Value
+  val None, Password, ChallengeResponse, Reserved = Value
+}
+import DebugModuleAuthType._
+
+object DebugModuleAccessType extends scala.Enumeration {
+  type DebugModuleAccessType = Value
+  val Access8Bit, Access16Bit, Access32Bit, Access64Bit, Access128Bit = Value
+}
+import DebugModuleAccessType._
+
+
+/** Parameters exposed to the top-level design, set based on
+  * external requirements, etc.
+  *
+  *  This object checks that the parameters conform to the 
+  *  full specification. The implementation which receives this
+  *  object can perform more checks on what that implementation
+  *  actually supports.
+  *  nComponents : The number of components to support debugging.
+  *  nDebugBusAddrSize : Size of the Debug Bus Address
+  *  nDebugRam Bytes: Size of the Debug RAM (depends on the XLEN of the machine).
+  *  debugRomContents: 
+  *  hasBusMaster: Whether or not a bus master should be included
+  *    The size of the accesses supported by the Bus Master. 
+  *  nSerialPorts : Number of serial ports to instantiate
+  *  authType : The Authorization Type
+  *  Number of cycles to assert ndreset when pulsed. 
+  **/
+
+
+case class DebugModuleConfig (
+  nComponents       : Int,
+  nDebugBusAddrSize : Int,
+  nDebugRamBytes    : Int,
+  debugRomContents  : Option[Seq[Byte]],
+  hasBusMaster : Boolean,
+  hasAccess128 : Boolean,
+  hasAccess64  : Boolean,
+  hasAccess32  : Boolean,
+  hasAccess16  : Boolean,
+  hasAccess8   : Boolean,
+  nSerialPorts : Int,
+  authType : DebugModuleAuthType,
+  nNDResetCycles : Int
+) {
+
+  if (hasBusMaster == false){
+    require (hasAccess128 == false)
+    require (hasAccess64  == false)
+    require (hasAccess32  == false)
+    require (hasAccess16  == false)
+    require (hasAccess8   == false)
+  }
+
+  require (nSerialPorts <= 8)
+
+  require ((nDebugBusAddrSize >= 5) && (nDebugBusAddrSize <= 7))
+
+  private val maxComponents = nDebugBusAddrSize match {
+    case 5 => (32*4)
+    case 6 => (32*32)
+    case 7 => (32*32)
+  }
+  require (nComponents > 0 && nComponents <= maxComponents)
+
+  private val maxRam = nDebugBusAddrSize match {
+    case 5 => (4 * 16)
+    case 6 => (4 * 16)
+    case 7 => (4 * 64)
+  }
+
+  require (nDebugRamBytes > 0 && nDebugRamBytes <= maxRam)
+
+  val hasHaltSum = (nComponents > 64) || (nSerialPorts > 0)
+
+  val hasDebugRom = debugRomContents match{
+    case Some(_) => true
+    case None => false
+  }
+
+  if (hasDebugRom) {
+    require (debugRomContents.size > 0)
+    require (debugRomContents.size <= 512)
+  }
+
+  require (nNDResetCycles > 0)
+
+}
+
+class DefaultDebugModuleConfig (val ncomponents : Int, val xlen:Int)
+    extends DebugModuleConfig(
+      nComponents = ncomponents,
+      nDebugBusAddrSize = 5,
+      nDebugRamBytes = xlen match{
+        case 32  => 28
+        case 64  => 40
+        case 128 => 64
+      },
+      debugRomContents = Some(DsbBusConsts.defaultRomContents),
+      hasBusMaster = false,
+      hasAccess128 = false, 
+      hasAccess64 = false, 
+      hasAccess32 = false, 
+      hasAccess16 = false, 
+      hasAccess8 = false, 
+      nSerialPorts = 0,
+      authType = DebugModuleAuthType.None,
+      nNDResetCycles = 1)
+
+case object DMKey extends Field[DebugModuleConfig]
+
+
+// *****************************************
+// Module Interfaces
+// 
+// *****************************************
+
+
+/** Structure to define the contents of a Debug Bus Request
+  */
+
+class DebugBusReq(addrBits : Int) extends Bundle {
+  val addr = UInt(width = addrBits)
+  val op   = UInt(width = DbBusConsts.dbOpSize)
+  val data = UInt(width = DbBusConsts.dbDataSize)
+
+  override def cloneType = new DebugBusReq(addrBits).asInstanceOf[this.type]
+}
+
+
+/** Structure to define the contents of a Debug Bus Response
+  */
+class DebugBusResp( ) extends Bundle {
+  val resp = UInt(width = DbBusConsts.dbRespSize)
+  val data = UInt(width = DbBusConsts.dbDataSize)
+}
+
+/** Structure to define the top-level DebugBus interface 
+  *  of DebugModule.
+  *  DebugModule is the consumer of this interface.
+  *  Therefore it has the 'flipped' version of this.
+  */
+
+class DebugBusIO(implicit val p: cde.Parameters) extends ParameterizedBundle()(p) {
+  val req = new  DecoupledIO(new DebugBusReq(p(DMKey).nDebugBusAddrSize))
+  val resp = new DecoupledIO(new DebugBusResp).flip()
+}
+
+// *****************************************
+// The Module 
+// 
+// *****************************************
+
+/** Parameterized version of the Debug Module defined in the
+  *  RISC-V Debug Specification 
+  *  
+  *  DebugModule is a slave to two masters:
+  *    The Debug Bus -- implemented as a generic Decoupled IO with request
+  *                   and response channels
+  *    The System Bus -- implemented as Uncached Tile Link.
+  *  
+  *  DebugModule is responsible for holding registers, RAM, and ROM
+  *      to support debug interactions, as well as driving interrupts
+  *      to a configurable number of components in the system.
+  *      It is also responsible for some reset lines.
+  */
+
+class DebugModule ()(implicit val p:cde.Parameters)
+    extends Module
+    with HasTileLinkParameters { 
+  val cfg = p(DMKey)
+
+  //--------------------------------------------------------------
+  // Import constants for shorter variable names
+  //--------------------------------------------------------------
+
+  import DbRegAddrs._
+  import DsbRegAddrs._
+  import DsbBusConsts._
+  import DbBusConsts._
+
+  //--------------------------------------------------------------
+  // Sanity Check Configuration For this implementation.
+  //--------------------------------------------------------------
+
+  require (cfg.nComponents <= 128)
+  require (cfg.nSerialPorts == 0)
+  require (cfg.hasBusMaster == false)
+  require (cfg.nDebugRamBytes <= 64)
+  require (cfg.authType == DebugModuleAuthType.None)
+
+  //--------------------------------------------------------------
+  // Private Classes (Register Fields)
+  //--------------------------------------------------------------
+
+  class RAMFields() extends Bundle {
+    val interrupt     = Bool()
+    val haltnot       = Bool()
+    val data          = Bits(width = 32)
+
+    override def cloneType = new RAMFields().asInstanceOf[this.type]    
+  }
+
+  class CONTROLFields() extends Bundle {
+    val interrupt     = Bool()
+    val haltnot       = Bool()
+    val reserved0     = Bits(width = 31-22 + 1)
+    val buserror      = Bits(width = 3)
+    val serial        = Bits(width = 3)
+    val autoincrement = Bool()
+    val access        = UInt(width = 3) 
+    val hartid        = Bits(width = 10)
+    val ndreset       = Bool()         
+    val fullreset     = Bool()
+
+    override def cloneType = new CONTROLFields().asInstanceOf[this.type]
+    
+  }
+
+  class DMINFOFields() extends Bundle {
+    val reserved0     = Bits(width = 2)
+    val abussize      = UInt(width = 7)
+    val serialcount   = UInt(width = 4)
+    val access128     = Bool()
+    val access64      = Bool()
+    val access32      = Bool()
+    val access16      = Bool()
+    val accesss8      = Bool()
+    val haltsum       = Bool()
+    val reserved1     = Bits(width = 3)
+    val authenticated = Bool()
+    val authbusy      = Bool()
+    val authtype      = UInt(width = 2)
+    val version       = UInt(width = 2)
+
+    override def cloneType = new DMINFOFields().asInstanceOf[this.type]
+    
+  }
+
+  class HALTSUMFields() extends Bundle {
+    val serialfull     = Bool()
+    val serialvalid    = Bool()
+    val acks           = Bits(width = 32)
+
+    override def cloneType = new HALTSUMFields().asInstanceOf[this.type]
+    
+  }
+
+  //--------------------------------------------------------------
+  // Module I/O
+  //--------------------------------------------------------------
+
+  val io = new Bundle {
+    val db = new DebugBusIO()(p).flip()
+    val debugInterrupts = Vec(cfg.nComponents, Bool()).asOutput
+    val tl = new ClientUncachedTileLinkIO().flip 
+    val ndreset    = Bool(OUTPUT)
+    val fullreset  = Bool(OUTPUT) 
+  }
+
+  //--------------------------------------------------------------
+  // Register & Wire Declarations
+  //--------------------------------------------------------------
+
+  // --- Debug Bus Registers
+  val CONTROLReset = Wire(new CONTROLFields())
+  val CONTROLWrEn = Wire(Bool())
+  val CONTROLReg = Reg(new CONTROLFields())
+  val CONTROLWrData = Wire (new CONTROLFields())
+  val CONTROLRdData = Wire (new CONTROLFields())
+  val ndresetCtrReg = Reg(UInt(cfg.nNDResetCycles))
+
+  val DMINFORdData = Wire (new DMINFOFields())
+
+  val HALTSUMRdData = Wire (new HALTSUMFields())
+
+  val RAMWrData = Wire (new RAMFields())
+  val RAMRdData = Wire (new RAMFields())
+
+  // --- System Bus Registers
+  
+  val SETHALTNOTWrEn = Wire(Bool())
+  val SETHALTNOTWrData = Wire(UInt(width = sbIdWidth))
+  val CLEARDEBINTWrEn = Wire(Bool())
+  val CLEARDEBINTWrData = Wire(UInt(width = sbIdWidth))
+
+  // --- Interrupt & Halt Notification Registers
+
+  val interruptRegs = Reg(init=Vec.fill(cfg.nComponents){Bool(false)})
+
+  val haltnotRegs     = Reg(init=Vec.fill(cfg.nComponents){Bool(false)})
+  val numHaltnotStatus = (Math.ceil(cfg.nComponents / 32)).toInt
+
+  val haltnotStatus = Wire(Vec(numHaltnotStatus, Bits(width = 32)))
+  val rdHaltnotStatus = Wire(Bits(width = 32))
+  
+  val haltnotSummary = Wire(Bits(width = 32))
+
+  // --- Debug RAM
+
+  // Since the access size from Debug Bus and System Bus may not be consistent,
+  // use the maximum to build the RAM, and then select as needed for the smaller
+  // size.
+
+  val dbRamDataWidth    = DbBusConsts.dbRamWordBits
+  val sbRamDataWidth    = tlDataBits
+  val dbRamAddrWidth    = log2Up((cfg.nDebugRamBytes * 8) / dbRamDataWidth) 
+  val sbRamAddrWidth    = log2Up((cfg.nDebugRamBytes * 8) / sbRamDataWidth)
+  val sbRamAddrOffset   = log2Up(tlDataBits/8)
+
+  val ramDataWidth = max(dbRamDataWidth, sbRamDataWidth)
+  val ramAddrWidth  = min(dbRamAddrWidth, sbRamAddrWidth)
+  val ramMem    = Mem(1 << ramAddrWidth , UInt(width=ramDataWidth))
+  val ramAddr   = Wire(UInt(width=ramAddrWidth))
+  val ramRdData = Wire(UInt(width=ramDataWidth))
+  val ramWrData = Wire(UInt(width=ramDataWidth))
+  val ramWrMask = Wire(UInt(width=ramDataWidth))
+  val ramWrEn   = Wire(Bool())
+
+  val dbRamAddr   = Wire(UInt(width=dbRamAddrWidth))
+  val dbRamRdData = Wire (UInt(width=dbRamDataWidth))
+  val dbRamWrData = Wire(UInt(width=dbRamDataWidth))
+  val dbRamWrEn   = Wire(Bool())
+  val dbRamRdEn   = Wire(Bool())
+
+  val sbRamAddr   = Wire(UInt(width=sbRamAddrWidth))
+  val sbRamRdData = Reg (UInt(width=sbRamDataWidth))
+  val sbRamWrData = Wire(UInt(width=sbRamDataWidth))
+  val sbRamWrEn   = Wire(Bool())
+  val sbRamRdEn   = Wire(Bool())
+
+  val sbRomRdData       = Wire(UInt(width=tlDataBits))
+  val sbRomAddrOffset   = log2Up(tlDataBits/8)
+
+  // --- Debug Bus Accesses
+
+  val dbRdEn   = Wire(Bool())
+  val dbWrEn   = Wire(Bool())
+  val dbRdData = Wire(UInt(width = DbBusConsts.dbDataSize))
+
+  val s_DB_READY :: s_DB_RESP :: Nil = Enum(Bits(), 2)
+  val dbStateReg = Reg(init = s_DB_READY)
+
+  val dbResult  = Wire(io.db.resp.bits)
+
+  val dbReq     = Wire(io.db.req.bits)
+  val dbRespReg = Reg(io.db.resp.bits) 
+
+  val rdCondWrFailure = Wire(Bool())
+  val dbWrNeeded = Wire(Bool())
+
+  // --- System Bus Access 
+  val sbAddr   = Wire(UInt(width=sbAddrWidth))
+  val sbRdData = Wire(UInt(width=tlDataBits))
+  val sbWrData = Wire(UInt(width=tlDataBits))
+  val sbWrMask = Wire(UInt(width=tlDataBits))
+  val sbWrEn   = Wire(Bool())
+  val sbRdEn   = Wire(Bool())
+
+  val stallFromDb = Wire(Bool())
+  val stallFromSb = Wire(Bool())
+  //--------------------------------------------------------------
+  // Interrupt Registers
+  //--------------------------------------------------------------
+  
+  for (component <- 0 until cfg.nComponents) {
+    io.debugInterrupts(component) := interruptRegs(component)
+  }
+
+  // Interrupt Registers are written by write to CONTROL or debugRAM addresses
+  // for Debug Bus, and cleared by writes to CLEARDEBINT by System Bus.
+  // It is "unspecified" what should happen if both
+  // SET and CLEAR happen at the same time. In this
+  // implementation, the SET wins.
+
+  for (component <- 0 until cfg.nComponents) {
+    when (CONTROLWrEn) {
+      when (CONTROLWrData.hartid === UInt(component)) {
+        interruptRegs(component) := interruptRegs(component) | CONTROLWrData.interrupt
+      }
+    }.elsewhen (dbRamWrEn) {
+      when (CONTROLReg.hartid === UInt(component)){
+        interruptRegs(component) := interruptRegs(component)  | RAMWrData.interrupt
+      }
+    }.elsewhen (CLEARDEBINTWrEn){
+      when (CLEARDEBINTWrData === UInt(component, width = sbIdWidth)) {
+        interruptRegs(component) := Bool(false)
+      }
+    }
+  }
+
+  //--------------------------------------------------------------
+  // Halt Notification Registers
+  //--------------------------------------------------------------
+
+  // Halt Notifications Registers are cleared by zero write to CONTROL or debugRAM addresses
+  // for Debug Bus, and set by write to SETHALTNOT by System Bus.
+  // It is "unspecified" what should happen if both
+  // SET and CLEAR happen at the same time. In this
+  // implementation, the SET wins.
+  
+  for (component <- 0 until cfg.nComponents) {
+    when (SETHALTNOTWrEn){
+      when (SETHALTNOTWrData === UInt(component, width = sbIdWidth)) {
+        haltnotRegs(component) := Bool(true)
+      }
+    } .elsewhen (CONTROLWrEn) {
+      when (CONTROLWrData.hartid === UInt(component)) {
+        haltnotRegs(component) := haltnotRegs(component) &  CONTROLWrData.haltnot
+      }
+    }.elsewhen (dbRamWrEn) {
+      when (CONTROLReg.hartid === UInt(component)){
+        haltnotRegs(component) := haltnotRegs(component)  &  RAMWrData.haltnot
+      }
+    }
+  }
+
+  for (ii <- 0 until numHaltnotStatus) {
+    for (jj <- 0 until 32) {
+      val component = ii * 32 + jj
+      if (component < cfg.nComponents){
+        haltnotStatus(ii)(jj) := haltnotRegs(component)
+      } else {
+        haltnotStatus(ii)(jj) := Bool(false)
+      }
+    }
+  }
+
+  haltnotSummary := Bits(0)
+  for (ii <- 0 until numHaltnotStatus) {
+    haltnotSummary(ii) := haltnotStatus(ii).orR
+  }
+
+  //--------------------------------------------------------------
+  // Other Registers 
+  //--------------------------------------------------------------
+
+  CONTROLReset.interrupt     := Bool(false) 
+  CONTROLReset.haltnot       := Bool(false) 
+  CONTROLReset.reserved0     := Bits(0)     
+  CONTROLReset.buserror      := Bits(0)
+  CONTROLReset.serial        := Bits(0)
+  CONTROLReset.autoincrement := Bool(false)
+  CONTROLReset.access        := UInt(DebugModuleAccessType.Access32Bit.id)
+  CONTROLReset.hartid        := Bits(0)
+  CONTROLReset.ndreset       := Bool(false)
+  CONTROLReset.fullreset     := Bool(false)
+
+  // Because this version of DebugModule doesn't
+  // support authentication, this entire register is
+  // Read-Only constant wires. 
+  DMINFORdData.reserved0     := Bits(0)
+  DMINFORdData.abussize      := UInt(0) // Not Implemented.
+  DMINFORdData.serialcount   := UInt(cfg.nSerialPorts)
+  DMINFORdData.access128     := Bool(cfg.hasAccess128)
+  DMINFORdData.access64      := Bool(cfg.hasAccess64)
+  DMINFORdData.access32      := Bool(cfg.hasAccess32)
+  DMINFORdData.access16      := Bool(cfg.hasAccess16)
+  DMINFORdData.accesss8      := Bool(cfg.hasAccess8)
+  DMINFORdData.haltsum       := Bool(cfg.hasHaltSum)
+  DMINFORdData.reserved1     := Bits(0)
+  DMINFORdData.authenticated := Bool(true) // Not Implemented.
+  DMINFORdData.authbusy      := Bool(false) // Not Implemented.
+  DMINFORdData.authtype      := UInt(cfg.authType.id)
+  DMINFORdData.version       := UInt(0)
+
+  HALTSUMRdData.serialfull  := Bool(false) // Not Implemented
+  HALTSUMRdData.serialvalid := Bool(false) // Not Implemented
+  HALTSUMRdData.acks        := haltnotSummary
+
+  //--------------------------------------------------------------
+  // Debug RAM Access (Debug Bus & System Bus)
+  //--------------------------------------------------------------
+
+  dbReq := io.db.req.bits
+  // Debug Bus RAM Access
+  // From Specification: Debug RAM is 0x00 - 0x0F
+  //                                  0x40 - 0x6F Not Implemented
+  dbRamAddr   := dbReq.addr( dbRamAddrWidth-1 , 0)
+  dbRamWrData := dbReq.data
+  sbRamAddr   := sbAddr(sbRamAddrWidth + sbRamAddrOffset - 1, sbRamAddrOffset)   
+  sbRamWrData := sbWrData
+
+  require (dbRamAddrWidth >= ramAddrWidth)    // SB accesses less than 32 bits Not Implemented.
+  val dbRamWrMask = Vec.fill(1 << (dbRamAddrWidth - ramAddrWidth)){Fill(dbRamDataWidth, UInt(1, width=1))}
+
+  if (dbRamDataWidth < ramDataWidth){
+
+    val dbRamSel = dbRamAddr(dbRamAddrWidth - ramAddrWidth - 1 , 0)
+    val rdDataWords = Vec.tabulate(1 << (dbRamAddrWidth - ramAddrWidth)){ ii =>
+      ramRdData((ii+1)*dbRamDataWidth - 1 , ii*dbRamDataWidth)}
+
+    dbRamWrMask := Vec.fill(1 << (dbRamAddrWidth - ramAddrWidth)){UInt(0, width = dbRamDataWidth)}
+    dbRamWrMask(dbRamSel) := Fill(dbRamDataWidth, UInt(1, width=1))
+    dbRamRdData := rdDataWords(dbRamSel)
+  } else {
+    dbRamRdData    := ramRdData
+  }
+
+  sbRamRdData := ramRdData
+
+  ramWrMask := Mux(sbRamWrEn, sbWrMask, dbRamWrMask.toBits())
+
+  assert (!((dbRamWrEn | dbRamRdEn) & (sbRamRdEn | sbRamWrEn)), "Stall logic should have prevented concurrent SB/DB RAM Access")
+
+  // Make copies of DB RAM data before writing.
+  val dbRamWrDataVec = Fill(1 << (dbRamAddrWidth - ramAddrWidth), dbRamWrData)
+  ramWrData := Mux(sbRamWrEn,
+    (ramWrMask & sbRamWrData          ) | (~ramWrMask & ramRdData),
+    (ramWrMask & dbRamWrDataVec.toBits) | (~ramWrMask & ramRdData))
+
+  ramAddr   := Mux(sbRamWrEn | sbRamRdEn, sbRamAddr,
+    dbRamAddr >> (dbRamAddrWidth - ramAddrWidth))
+
+  ramRdData := ramMem(ramAddr)
+  when (ramWrEn) { ramMem(ramAddr) := ramWrData }
+
+  ramWrEn := sbRamWrEn | dbRamWrEn
+  
+  //--------------------------------------------------------------
+  // Debug Bus Access
+  //--------------------------------------------------------------
+
+  // 0x00 - 0x0F Debug RAM
+  // 0x10 - 0x1B Registers
+  // 0x1C - 0x3B Halt Notification Registers
+  // 0x3C - 0x3F Registers
+  // 0x40 - 0x6F Debug RAM
+
+
+  // -----------------------------------------
+  // DB Access Write Decoder
+
+  CONTROLWrData := new CONTROLFields().fromBits(dbReq.data)
+  RAMWrData     := new RAMFields().fromBits(dbReq.data)
+
+  dbRamWrEn  := Bool(false)
+  CONTROLWrEn := Bool(false)
+  when ((dbReq.addr >> 4) === Bits(0)) {                   // 0x00 - 0x0F Debug RAM
+    dbRamWrEn := dbWrEn
+   }.elsewhen (dbReq.addr === DMCONTROL) {
+    CONTROLWrEn  := dbWrEn
+  }.otherwise {
+    //Other registers/RAM are Not Implemented.
+  }
+
+  when (reset) {
+    CONTROLReg := CONTROLReset
+    ndresetCtrReg := UInt(0)
+  }.elsewhen (CONTROLWrEn) {
+    // interrupt handled in other logic
+    // haltnot   handled in other logic
+    if (cfg.hasBusMaster){
+      // buserror is set 'until 0 is written to any bit in this field'. 
+      CONTROLReg.buserror      := Mux((CONTROLWrData.buserror === SInt(-1).toBits), CONTROLReg.buserror, UInt(0))
+      CONTROLReg.autoincrement := CONTROLWrData.autoincrement
+      CONTROLReg.access        := CONTROLWrData.access
+    }
+    if (cfg.nSerialPorts > 0){
+      CONTROLReg.serial        := CONTROLWrData.serial
+    }
+    CONTROLReg.hartid        := CONTROLWrData.hartid
+    CONTROLReg.fullreset     := CONTROLReg.fullreset | CONTROLWrData.fullreset
+    when (CONTROLWrData.ndreset){
+      ndresetCtrReg := UInt(cfg.nNDResetCycles)
+    }.otherwise {
+      ndresetCtrReg := Mux(ndresetCtrReg === UInt(0) , UInt(0), ndresetCtrReg - UInt(1)) 
+    }
+  }.otherwise {
+    ndresetCtrReg := Mux(ndresetCtrReg === UInt(0) , UInt(0), ndresetCtrReg - UInt(1))
+  }
+
+  // -----------------------------------------
+  // DB Access Read Mux
+ 
+  CONTROLRdData := CONTROLReg;
+  CONTROLRdData.interrupt := interruptRegs(CONTROLReg.hartid)
+  CONTROLRdData.haltnot   := haltnotRegs(CONTROLReg.hartid)
+  CONTROLRdData.ndreset   := ndresetCtrReg.orR
+
+  RAMRdData.interrupt := interruptRegs(CONTROLReg.hartid)
+  RAMRdData.haltnot   := haltnotRegs(CONTROLReg.hartid)
+  RAMRdData.data      := dbRamRdData
+
+  dbRdData := UInt(0)
+
+  // Higher numbers of numHaltnotStatus Not Implemented.
+  // This logic assumes only up to 128 components.
+  rdHaltnotStatus := Bits(0)
+  for (ii <- 0 until numHaltnotStatus) {
+    when (dbReq.addr === UInt(ii)) {
+      rdHaltnotStatus := haltnotStatus(ii)
+    }
+  }
+
+  dbRamRdEn := Bool(false)
+  when ((dbReq.addr >> 4) === Bits(0)) {       // 0x00 - 0x0F Debug RAM
+    dbRdData  := RAMRdData.toBits()
+    dbRamRdEn := dbRdEn
+  }.elsewhen (dbReq.addr === DMCONTROL) {
+    dbRdData := CONTROLRdData.toBits()
+  }.elsewhen (dbReq.addr === DMINFO) {
+    dbRdData := DMINFORdData.toBits()
+  }.elsewhen (dbReq.addr === HALTSUM) {
+    if (cfg.hasHaltSum){
+      dbRdData := HALTSUMRdData.toBits()
+    } else {
+      dbRdData := UInt(0)
+    }
+  }.elsewhen ((dbReq.addr >> 2) === UInt(7)) { // 0x1C - 0x1F Haltnot
+    dbRdData := rdHaltnotStatus
+  } .otherwise {
+    //These Registers are not implemented in this version of DebugModule:
+    // AUTHDATA0
+    // AUTHDATA1
+    // SERDATA
+    // SERSTATUS
+    // SBUSADDRESS0
+    // SBUSADDRESS1
+    // SBDATA0     
+    // SBDATA1     
+    // SBADDRESS2  
+    // SBDATA2     
+    // SBDATA3
+    // 0x20 - 0x3B haltnot
+    // Upper bytes of Debug RAM.
+    dbRdData := UInt(0)
+  }
+    
+  // Conditional write fails if MSB is set of the read data.
+  rdCondWrFailure := dbRdData(dbDataSize - 1 ) &&
+  (dbReq.op === db_OP_READ_COND_WRITE)
+
+  dbWrNeeded := (dbReq.op === db_OP_READ_WRITE) ||
+  ((dbReq.op === db_OP_READ_COND_WRITE) && ~rdCondWrFailure)
+
+  // This is only relevant at end of s_DB_READ.
+  dbResult.resp := Mux(rdCondWrFailure,
+    db_RESP_FAILURE,
+    db_RESP_SUCCESS)
+  dbResult.data := dbRdData
+
+  // -----------------------------------------
+  // DB Access State Machine Decode (Combo)
+  io.db.req.ready := !stallFromSb && ((dbStateReg === s_DB_READY) ||
+    (dbStateReg === s_DB_RESP && io.db.resp.fire()))
+
+  io.db.resp.valid := (dbStateReg === s_DB_RESP)
+  io.db.resp.bits  := dbRespReg
+
+  dbRdEn := io.db.req.fire()
+  dbWrEn := dbWrNeeded && io.db.req.fire()
+
+  // -----------------------------------------
+  // DB Access State Machine Update (Seq)
+
+  when (dbStateReg === s_DB_READY){
+    when (io.db.req.fire()){
+      dbStateReg := s_DB_RESP
+      dbRespReg := dbResult
+    }
+  } .elsewhen (dbStateReg === s_DB_RESP){
+    when (io.db.req.fire()){
+      dbStateReg := s_DB_RESP
+      dbRespReg := dbResult
+    }.elsewhen (io.db.resp.fire()){
+      dbStateReg := s_DB_READY
+    }
+  }
+
+  
+  //--------------------------------------------------------------
+  // Debug ROM
+  //--------------------------------------------------------------
+
+  sbRomRdData := UInt(0)
+  if (cfg.hasDebugRom) {
+    // Inspired by ROMSlave
+    val romContents = cfg.debugRomContents.get
+    val romByteWidth = tlDataBits / 8
+    val romRows =  Math.ceil((romContents.size + romByteWidth)/romByteWidth).toInt
+    val romMem = Vec.tabulate(romRows) { ii =>
+      val slice = romContents.slice(ii*romByteWidth, (ii+1)*romByteWidth)
+      UInt(slice.foldRight(BigInt(0)) { case (x,y) => ((y << 8) + (x.toInt & 0xFF))}, width = romByteWidth*8)
+    }
+
+    val sbRomRdAddr = Wire(UInt())
+
+    if (romRows == 1) {
+      sbRomRdAddr := UInt(0)
+    } else {
+      sbRomRdAddr := sbAddr(log2Up(romRows) + sbRomAddrOffset - 1, sbRomAddrOffset)
+    }
+    sbRomRdData := romMem (sbRomRdAddr)
+  }
+
+  //--------------------------------------------------------------
+  // System Bus Access
+  //--------------------------------------------------------------
+
+
+  // -----------------------------------------
+  // SB Access Write Decoder
+
+  sbRamWrEn  := Bool(false)
+  SETHALTNOTWrEn := Bool(false)
+  CLEARDEBINTWrEn := Bool(false)
+
+  if (tlDataBits == 32) {
+    SETHALTNOTWrData := sbWrData
+    CLEARDEBINTWrData := sbWrData
+    when (sbAddr(11, 8)   === UInt(4)){ // 0x400-0x4ff is Debug RAM
+      sbRamWrEn := sbWrEn
+      sbRamRdEn := sbRdEn
+    }.elsewhen (sbAddr === SETHALTNOT){
+      SETHALTNOTWrEn := sbWrEn
+    }.elsewhen (sbAddr === CLEARDEBINT){
+      CLEARDEBINTWrEn := sbWrEn
+    }.otherwise {
+      //Other registers/RAM are Not Implemented.
+    }
+  } else {
+
+    // Pick out the correct word based on the address.
+    val sbWrDataWords = Vec.tabulate (tlDataBits / 32) {ii => sbWrData((ii+1)*32 - 1, ii*32)}
+    val sbWrMaskWords = Vec.tabulate(tlDataBits/32) {ii => sbWrMask ((ii+1)*32 -1, ii*32)}
+
+    val sbWrSelTop = log2Up(tlDataBits/8)
+    val sbWrSelBottom = 2
+
+    SETHALTNOTWrData  := sbWrDataWords(SETHALTNOT(sbWrSelTop, sbWrSelBottom))
+    CLEARDEBINTWrData := sbWrDataWords(CLEARDEBINT(sbWrSelTop, sbWrSelBottom))
+
+    when (sbAddr(11,8) === UInt(4)){ //0x400-0x4ff is Debug RAM
+      sbRamWrEn := sbWrEn
+      sbRamRdEn := sbRdEn
+    }
+ 
+    SETHALTNOTWrEn := sbAddr(sbAddrWidth - 1, sbWrSelTop) === SETHALTNOT(sbAddrWidth-1, sbWrSelTop) &&
+    sbWrMaskWords(SETHALTNOT(sbWrSelTop, sbWrSelBottom)).orR &&
+    sbWrEn
+
+    CLEARDEBINTWrEn := sbAddr(sbAddrWidth - 1, sbWrSelTop) === CLEARDEBINT(sbAddrWidth-1, sbWrSelTop) &&
+    sbWrMaskWords(CLEARDEBINT(sbWrSelTop, sbWrSelBottom)).orR &&
+    sbWrEn
+
+  }
+
+  // -----------------------------------------
+  // SB Access Read Mux
+ 
+  sbRdData := UInt(0)
+  sbRamRdEn := Bool(false)
+
+  dbRamRdEn := Bool(false)
+  when (sbAddr(11, 8) === UInt(4)) {                                 //0x400-0x4FF Debug RAM
+    sbRdData  := sbRamRdData
+    sbRamRdEn := sbRdEn
+  }.elsewhen (sbAddr(11,8) === UInt(8) || sbAddr(11,8) === UInt(9)){ //0x800-0x9FF Debug ROM
+    if (cfg.hasDebugRom) {
+      sbRdData := sbRomRdData
+    } else {
+      sbRdData := UInt(0)
+    }
+  }. otherwise {
+    // All readable registers are Not Implemented.
+    sbRdData := UInt(0)
+  }
+
+  // -----------------------------------------
+  // SB Access State Machine -- based on BRAM Slave
+
+  val sbAcqReg = Reg(io.tl.acquire.bits)
+  val sbAcqValidReg = Reg(init = Bool(false))
+
+  val (sbReg_get :: sbReg_getblk :: sbReg_put :: sbReg_putblk :: Nil) = Seq(
+    Acquire.getType, Acquire.getBlockType, Acquire.putType, Acquire.putBlockType
+  ).map(sbAcqReg.isBuiltInType _)
+
+  val sbMultibeat = sbReg_getblk
+
+
+  val sbBeatInc1 = sbAcqReg.addr_beat + UInt(1)
+ 
+  val sbLast = (sbAcqReg.addr_beat === UInt(tlDataBeats - 1))
+
+  sbAddr := sbAcqReg.full_addr()
+  sbRdEn := (sbAcqValidReg && (sbReg_get || sbReg_getblk))
+  sbWrEn := (sbAcqValidReg && (sbReg_put || sbReg_putblk))
+  sbWrData := sbAcqReg.data
+  sbWrMask := sbAcqReg.full_wmask()
+
+  // -----------------------------------------
+  // SB Access State Machine Update (Seq)
+
+  when (io.tl.acquire.fire()){
+    sbAcqReg       := io.tl.acquire.bits
+    sbAcqValidReg  := Bool(true)
+  } .elsewhen (io.tl.grant.fire()) {
+    when (sbMultibeat){
+      sbAcqReg.addr_beat := sbBeatInc1
+      when (sbLast) {
+        sbAcqValidReg := Bool(false)
+      }
+    } . otherwise {
+      sbAcqValidReg := Bool(false)
+    }
+  }
+  
+
+  io.tl.grant.valid := sbAcqValidReg
+  io.tl.grant.bits := Grant(
+    is_builtin_type = Bool(true),
+    g_type = sbAcqReg.getBuiltInGrantType(),
+    client_xact_id = sbAcqReg.client_xact_id,
+    manager_xact_id = UInt(0),
+    addr_beat = sbAcqReg.addr_beat,
+    data = sbRdData
+  )
+
+  stallFromDb := Bool(false) // SB always wins, and DB latches its read data so it is not necessary for SB to wait
+
+  stallFromSb := sbRamRdEn || sbRamWrEn // pessimistically assume that DB/SB are going to conflict on the RAM,
+                                        // and SB doesn't latch its read data to it is necessary for DB hold
+                                        // off while SB is accessing the RAM and waiting to send its result.
+
+  val sbStall = (sbMultibeat & !sbLast) || (io.tl.grant.valid  && !io.tl.grant.ready) || stallFromDb
+
+  io.tl.acquire.ready := !sbStall
+
+  //--------------------------------------------------------------
+  // Misc. Outputs
+  //--------------------------------------------------------------
+
+  io.ndreset   := ndresetCtrReg.orR
+  io.fullreset := CONTROLReg.fullreset
+
+}