# Editing GSD File for Address Size Allocation in TIA Portal **URL:** \ **Category:** Controls & Vision\ **Tags:** profibus, profinet\ **Created:** [February 3, 2026, 8:47am UTC](https://community.br-automation.com/t/editing-gsd-file-for-address-size-allocation-in-tia-portal/9976 "2026-02-03T08:47:54Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Kavinaya](https://avatars.discourse-cdn.com/v4/letter/k/FF8800/32.png) [@Kavinaya](https://community.br-automation.com/u/Kavinaya)\ **Post date:** [February 3, 2026, 8:47am UTC](https://community.br-automation.com/t/editing-gsd-file-for-address-size-allocation-in-tia-portal/9976/1 "2026-02-03T08:47:54Z")
Hello everyone, One of our customers is working with B&R I/O modules connected to a Siemens controller in TIA Portal, and they’ve noticed some issues with the way addresses are being allocated from the GSD file. - For **X20DI9371** , the system allocates **3 bytes** (including diagnostic bytes), but they only require **2 bytes** without diagnostics for each module. - For **X20DO9322** , the allocation includes both **input and output addresses** , whereas they only need **output allocation**. **Is it possible to edit the GSD file to adjust the size allocation in the address mapping so that it matches these requirements?** Any guidance, experiences, or suggestions from the community would be greatly appreciated. Thanks in advance! ---
**Author:** ![oliver\_D](https://dub1.discourse-cdn.com/brcommunity/user_avatar/community.br-automation.com/oliver_d/32/257_2.png) [@oliver\_D](https://community.br-automation.com/u/oliver_D)\ **Post date:** [February 3, 2026, 9:10am UTC](https://community.br-automation.com/t/editing-gsd-file-for-address-size-allocation-in-tia-portal/9976/2 "2026-02-03T09:10:07Z")
Hello, unfortunatly no. The firmware of the module will send the 3 bytes and therefor an edit of the GDSML file will not help EDIT: Profinet is a Ethernet based bus system with quite a high bandwidth so this extra bytes should not matter best regards Oliver