1 files changed, 64 insertions, 0 deletions

diff --git a/hdl/echo_arbiter.sv b/hdl/echo_arbiter.sv
new file mode 100644
index 0000000..1c27e31
--- /dev/null
+++ b/hdl/echo_arbiter.sv
@@ -0,0 +1,64 @@
+`include "defs.svh"
+
+module echo_arbiter
+    (   input   bit         clock
+    ,   input   bit         reset
+
+    ,   output  bit         in0_ready
+    ,   input   bit         in0_valid
+    ,   input   uart_byte_t in0_data
+
+    ,   output  bit         in1_ready
+    ,   input   bit         in1_valid
+    ,   input   uart_byte_t in1_data
+
+    ,   input   bit         out_ready
+    ,   output  bit         out_valid
+    ,   output  uart_byte_t out_data
+    );
+
+    bit         in0_hold_valid;
+    uart_byte_t in0_hold;
+
+    bit         in1_hold_valid;
+    uart_byte_t in1_hold;
+
+    always @(posedge clock) begin
+        if (reset) begin
+            in0_ready = 0;
+            in1_ready = 0;
+            out_valid = 0;
+            out_data = 0;
+            in0_hold_valid = 0;
+            in0_hold = 0;
+            in1_hold_valid = 0;
+            in1_hold = 0;
+        end else begin
+            if (out_ready) out_valid = 0;
+            if (in0_ready && in0_valid) begin
+                in0_hold_valid = 1;
+                in0_hold = in0_data;
+            end
+            if (in1_ready && in1_valid) begin
+                in1_hold_valid = 1;
+                in1_hold = in1_data;
+            end
+
+            if (!out_valid) begin
+                if (in0_hold_valid) begin
+                    out_valid = 1;
+                    out_data = in0_hold;
+                    in0_hold_valid = 0;
+                end else if (in1_hold_valid) begin
+                    out_valid = 1;
+                    out_data = in1_hold;
+                    in1_hold_valid = 0;
+                end
+            end
+
+            in0_ready = !in0_hold_valid;
+            in1_ready = !in1_hold_valid;
+        end
+    end
+
+endmodule