Asynchronous Reset (#1011)

Fixes #219

* Adds AsyncResetType (similar to ClockType)
* Registers with reset signal of type AsyncResetType are async reset
  registers
* Registers with async reset can only be reset to literal values
* Add initialization logic for async reset registers

1 files changed, 6 insertions, 0 deletions

diff --git a/src/main/proto/firrtl.proto b/src/main/proto/firrtl.proto
index 7be042ab..8f115c5e 100644
--- a/src/main/proto/firrtl.proto
+++ b/src/main/proto/firrtl.proto
@@ -262,6 +262,10 @@ message Firrtl {
       // Empty.
     }
 
+    message AsyncResetType {
+      // Empty.
+    }
+
     message BundleType {
       message Field {
         // Required.
@@ -299,6 +303,7 @@ message Firrtl {
       VectorType vector_type = 6;
       FixedType fixed_type = 7;
       AnalogType analog_type = 8;
+      AsyncResetType async_reset_type = 9;
     }
   }
 
@@ -425,6 +430,7 @@ message Firrtl {
         OP_SHIFT_BINARY_POINT_LEFT = 35;
         OP_SHIFT_BINARY_POINT_RIGHT = 36;
         OP_SET_BINARY_POINT = 37;
+        OP_AS_ASYNC_RESET = 38;
       }
 
       // Required.