diff --git a/src/main/scala/devices/msi/MSIMaster.scala b/src/main/scala/devices/msi/MSIMaster.scala
new file mode 100644
index 0000000..185cea4
--- /dev/null
+++ b/src/main/scala/devices/msi/MSIMaster.scala
@@ -0,0 +1,75 @@
+// See LICENSE for license details.
+
+package sifive.blocks.devices.msi
+
+import Chisel._
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.interrupts._
+import freechips.rocketchip.tilelink._
+import freechips.rocketchip.util.leftOR
+
+case class MSITarget(address: BigInt, spacing: Int, number: Int)
+{
+  require (number >= 0)
+  require (address >= 0)
+}
+
+class MSIMaster(targets: Seq[MSITarget])(implicit p: Parameters) extends LazyModule
+{
+  val masterNode = TLClientNode(Seq(TLClientPortParameters(Seq(TLClientParameters("MSI Master", sourceId = IdRange(0,2))))))
+
+  // A terminal interrupt node of flexible number
+  val intNode = IntNexusNode(
+    sourceFn = { _ => IntSourcePortParameters(Seq(IntSourceParameters(1, Nil))) },
+    sinkFn   = { _ => IntSinkPortParameters(Seq(IntSinkParameters())) },
+    inputRequiresOutput = false)
+
+  lazy val module = new LazyModuleImp(this) {
+    val (io, masterEdge) = masterNode.out(0)
+    val interrupts = intNode.in.flatMap { case (i, e) => i.take(e.source.num) }
+
+    // Construct a map of the addresses to update for interrupts
+    val targetMap = targets.flatMap { case MSITarget(address, spacing, number) =>
+      address until (address+spacing*number) by spacing
+    } .map { addr =>
+      val m = masterEdge.manager.find(addr)
+      require (m.isDefined, s"MSIMaster ${name} was pointed at address 0x${addr}%x which does not exist")
+      require (m.get.supportsPutFull.contains(1), s"MSIMaster ${name} requires device ${m.get.name} supportPutFull of 1 byte (${m.get.supportsPutFull})")
+      UInt(addr)
+    }.take(interrupts.size max 1)
+
+    require (interrupts.size <= targetMap.size, s"MSIMaster ${name} has more interrupts (${interrupts.size}) than addresses to use (${targetMap.size})")
+    require (intNode.out.isEmpty, s"MSIMaster ${name} intNode is not a source!")
+
+    val busy    = RegInit(Bool(false))
+    val remote  = RegInit(UInt(0, width=interrupts.size max 1))
+    val local   = if (interrupts.isEmpty) UInt(0) else Cat(interrupts.reverse)
+    val pending = remote ^ local
+    val select  = ~(leftOR(pending) << 1) & pending
+
+    io.a.valid := pending.orR && !busy
+    io.a.bits := masterEdge.Put(
+      fromSource = UInt(0),
+      toAddress  = Mux1H(select, targetMap),
+      lgSize     = UInt(0),
+      data       = (select & local).orR)._2
+
+    // When A is sent, toggle our model of the remote state
+    when (io.a.fire()) {
+      remote := remote ^ select
+      busy   := Bool(true)
+    }
+
+    // Sink D messages to clear busy
+    io.d.ready := Bool(true)
+    when (io.d.fire()) {
+      busy := Bool(false)
+    }
+
+    // Tie off unused channels
+    io.b.ready := Bool(false)
+    io.c.valid := Bool(false)
+    io.e.valid := Bool(false)
+  }
+}