diff --git a/assets/datapath.svg b/assets/datapath.svg
index 17cf588..038d36d 100644
--- a/assets/datapath.svg
+++ b/assets/datapath.svg
@@ -217,6 +217,27 @@ text.value-label {
        height="241.3898"
        x="0"
        y="1.1471907e-05" />
+    <g
+       class="wires"
+       id="control-ecall">
+      <path
+         class="wire"
+         style="marker-start:url(#Junction)"
+         d="m 123.20621,42.238088 0.0387,16.165581"
+         id="path17"
+         sodipodi:nodetypes="cc" />
+      <text
+         class="value-label"
+         xml:space="preserve"
+         x="123.22873"
+         y="51.644066"
+         id="text711-6-1-5"><tspan
+           sodipodi:role="line"
+           id="tspan709-4-3-3"
+           x="123.22873"
+           y="51.644066"
+           style="text-anchor:middle">Label</tspan></text>
+    </g>
   </g>
   <g
      inkscape:groupmode="layer"
@@ -368,12 +389,12 @@ text.value-label {
       <text
          class="value-label"
          xml:space="preserve"
-         x="121.45955"
+         x="148.97595"
          y="20.96104"
          id="text711-6-6-5-6-8-6-9-2-6"><tspan
            sodipodi:role="line"
            id="tspan709-4-2-8-2-4-2-9-0-6"
-           x="121.45955"
+           x="148.97595"
            y="20.96104"
            style="text-anchor:middle">Label</tspan></text>
     </g>
diff --git a/src/ui/datapath.ts b/src/ui/datapath.ts
index b0c1dc1..2b99566 100644
--- a/src/ui/datapath.ts
+++ b/src/ui/datapath.ts
@@ -83,6 +83,7 @@ const opCodeNames = new TruthTable([
     [["1101111"], "jal"],
     [["0110111"], "lui"],
     [["0010111"], "auipc"],
+    [["1110011"], "ecall/ebreak"],
 ])
 
 const aluOpNames = new TruthTable([
@@ -128,6 +129,11 @@ const writeSrcDescriptions = new TruthTable([
     [["11"], "PC + upper imm to register (auipc)"],
 ])
 
+const ecallDescriptions = new TruthTable([
+    [["00"], "no syscall"],
+    [["01"], "ecall instruction"],
+    [["10"], "ebreak instruction"],
+])
 
 export const riscv32DataPath: DataPath = {
     name: "RISC-V 32-bit",
@@ -287,6 +293,12 @@ export const riscv32DataPath: DataPath = {
             tooltip: `${sim.control.jalr} (${sim.control.jalr ? "do jump register" : "don't jump register"})`,
             powered: sim.control.jalr != 0,
         }),
+        "#control-ecall": (sim) => ({
+            description: "Ecall: Signal the system for a syscall or debugger breakpoint",
+            tooltip: `${sim.control.ecall.toString("unsigned")} (${ecallDescriptions.match(sim.control.ecall)})`,
+            powered: sim.control.ecall.toInt() != 0n,
+            label: sim.control.ecall.toNumber() ? sim.control.ecall.toString("unsigned") : undefined,
+        }),
         "#immGen-immediate": (sim) => ({
             tooltip: bitsToAll(sim.immGen.immediate),
             label: sim.immGen.immediate.toString("signed"),