diff --git a/ARM.SDS.pdsc b/ARM.SDS.pdsc
index 2eb5086..221b478 100644
--- a/ARM.SDS.pdsc
+++ b/ARM.SDS.pdsc
@@ -15,6 +15,8 @@
   <releases>
     <release version="2.2.0-dev">
       Active development ...
+      Template:
+      - Corestone-300/320: Fixed SDS I/O VSI driver to return correct error and status codes (SDSIO_ERROR, SDSIO_EOS)
     </release>
   </releases>
 
diff --git a/template/Board/Corstone-300/vsi/python/arm_vsi3.py b/template/Board/Corstone-300/vsi/python/arm_vsi3.py
index b5ebfbd..5a45264 100644
--- a/template/Board/Corstone-300/vsi/python/arm_vsi3.py
+++ b/template/Board/Corstone-300/vsi/python/arm_vsi3.py
@@ -88,7 +88,7 @@ def app(self, message, *args, **kwargs):
 # 'No limit' for idx-end
 NO_LIMIT = 0x7FFFFFFF
 
-# SDS I/O error/status codes (32-bit two's‑complement, used in the ARGUMENT register)
+# SDS I/O error/status codes (32-bit two's-complement, used in the ARGUMENT register)
 SDSIO_ERROR = (-1 & 0xFFFFFFFF)  # -1
 SDSIO_EOS   = (-6 & 0xFFFFFFFF)  # -6
 
diff --git a/template/Board/Corstone-320/vsi/python/arm_vsi3.py b/template/Board/Corstone-320/vsi/python/arm_vsi3.py
index 9d23c0d..5a45264 100644
--- a/template/Board/Corstone-320/vsi/python/arm_vsi3.py
+++ b/template/Board/Corstone-320/vsi/python/arm_vsi3.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2025 Arm Limited. All rights reserved.
+# Copyright (c) 2025-2026 Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: Apache-2.0
 #
@@ -88,6 +88,10 @@ def app(self, message, *args, **kwargs):
 # 'No limit' for idx-end
 NO_LIMIT = 0x7FFFFFFF
 
+# SDS I/O error/status codes (32-bit two's-complement, used in the ARGUMENT register)
+SDSIO_ERROR = (-1 & 0xFFFFFFFF)  # -1
+SDSIO_EOS   = (-6 & 0xFFFFFFFF)  # -6
+
 class IndexAllocator:
     """
     Hands out the next SDS index.
@@ -415,12 +419,12 @@ def processCOMMAND(command):
 
     elif command == 3: # Write
         # Return data length or SDSIO_ERROR
-        ARGUMENT = len(Data) if Stream.write(STREAM_ID, Data) else -1
+        ARGUMENT = len(Data) if Stream.write(STREAM_ID, Data) else SDSIO_ERROR
 
     elif command == 4: # Read
         # Return data length or SDSIO_EOS
         Data, eof = Stream.read(STREAM_ID, ARGUMENT)
-        ARGUMENT = len(Data) if not eof else -6
+        ARGUMENT = len(Data) if not eof else SDSIO_EOS
 
     return command
 
@@ -570,4 +574,3 @@ def wrRegs(index, value):
 
 
 ## @}
-