diff --git a/src/instruction.rs b/src/instruction.rs
index eaffe20..1a8777e 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -192,11 +192,12 @@ impl<'a> Instruction<'a> {
                 buffer[4..4 + ids.len()].copy_from_slice(ids);
                 Ok(4 + u16::try_from(ids.len()).map_err(|_| Error::Unknown)?)
             }
-            SyncWrite {
-                addr: _,
-                len: _,
-                data: _,
-            } => unimplemented!(),
+            SyncWrite { addr, len, data } if buffer.len() >= 4 + data.len() => {
+                buffer[..2].copy_from_slice(&addr.to_le_bytes());
+                buffer[2..4].copy_from_slice(&len.to_le_bytes());
+                buffer[4..4 + data.len()].copy_from_slice(data);
+                Ok(4 + u16::try_from(data.len()).map_err(|_| Error::Unknown)?)
+            }
             BulkRead { data: _ } => unimplemented!(),
             BulkWrite { data: _ } => unimplemented!(),
             FastBulkRead { data: _ } => unimplemented!(),