diff --git a/hyphae/vm.toml b/hyphae/vm.toml
index b445a25..c33aecf 100644
--- a/hyphae/vm.toml
+++ b/hyphae/vm.toml
@@ -641,6 +641,20 @@ character byte.
 Requires mutable access to input address.
 """
 
+[[instructions]]
+name = "ntobv"
+args = ["src"]
+output = ""
+description = """
+The ntobv instruction accepts a single number input. This operand is overwritten
+by a new number datum that represents the inexact form of the source number.
+
+The inexact form is a normalization of fraction or scientific notation datum to
+float datum casted to ByteVector datum.
+
+Requires mutable access to input address.
+"""
+
 [[instructions]]
 name = "ntoc"
 args = ["src"]