Add ExternalInterruptArrayPlugin

src/main/scala/vexriscv/plugin/ExternalInterruptArrayPlugin.scala

@@ -0,0 +1,21 @@
+package vexriscv.plugin
+
+import spinal.core._
+import vexriscv.VexRiscv
+
+class ExternalInterruptArrayPlugin(arrayWidth : Int = 32) extends Plugin[VexRiscv]{
+  var externalInterruptArray : Bits = null
+
+  override def setup(pipeline: VexRiscv): Unit = {
+    externalInterruptArray = in(Bits(arrayWidth bits)).setName("externalInterruptArray")
+  }
+
+  override def build(pipeline: VexRiscv): Unit = {
+    val csr = pipeline.service(classOf[CsrPlugin])
+    val mask = Reg(Bits(arrayWidth bits)) init(0)
+    val pendings = mask & RegNext(externalInterruptArray)
+    csr.externalInterrupt.asDirectionLess() := pendings.orR
+    csr.rw(0x330, mask)
+    csr.r(0x360, pendings)
+  }
+}