# Tag will read bit status from plc but wont write **URL:** \ **Category:** Ignition\ **Created:** [May 23, 2018, 12:44pm UTC](https://forum.inductiveautomation.com/t/tag-will-read-bit-status-from-plc-but-wont-write/18133 "2018-05-23T12:44:03Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![markm](https://avatars.discourse-cdn.com/v4/letter/m/9de053/32.png) [@markm](https://forum.inductiveautomation.com/u/markm)\ **Post date:** [May 23, 2018, 12:44pm UTC](https://forum.inductiveautomation.com/t/tag-will-read-bit-status-from-plc-but-wont-write/18133/1 "2018-05-23T12:44:03Z")
I have a UDT that matched the PLC UDT and I have verified the tag path. I have also set the bi directional option for this tag. the problem is that if i toggle the bit in ignition the plc does not see it, but if i toggle the bit in the plc ignition sees it change state. This setup works elsewhere but i cant figure out why this is happing ---
**Author:** ![automatisation](https://avatars.discourse-cdn.com/v4/letter/a/94ad74/32.png) [@automatisation](https://forum.inductiveautomation.com/u/automatisation)\ **Post date:** [May 23, 2018, 1:12pm UTC](https://forum.inductiveautomation.com/t/tag-will-read-bit-status-from-plc-but-wont-write/18133/2 "2018-05-23T13:12:28Z")
Has the access rights for the instancied tag have been overwritten and set to Read Only ? ---
**Author:** ![markm](https://avatars.discourse-cdn.com/v4/letter/m/9de053/32.png) [@markm](https://forum.inductiveautomation.com/u/markm)\ **Post date:** [May 23, 2018, 1:40pm UTC](https://forum.inductiveautomation.com/t/tag-will-read-bit-status-from-plc-but-wont-write/18133/3 "2018-05-23T13:40:59Z")
No but i did find that when i set my usage to output in studio 5000 you can no longer write to that tag, and since it is a UDT i cannot isolate a single tag within the udt. I was passing the value from a local UDT tag to global using this method but all other functions were interrupted. ---
**Author:** ![witman](https://avatars.discourse-cdn.com/v4/letter/w/d2c977/32.png) [@witman](https://forum.inductiveautomation.com/u/witman)\ **Post date:** [May 25, 2018, 4:53am UTC](https://forum.inductiveautomation.com/t/tag-will-read-bit-status-from-plc-but-wont-write/18133/4 "2018-05-25T04:53:52Z")
As you’ve found, I believe outputs are read-only in later versions of RSLogix 5000 / Studio 5000. I’m not sure I understand exactly what you’re doing, but if the issue is you want to pass this UDT from an add on instruction to a global tag, specifying it as an In/Out type (passes by reference so AOI works directly on global tag rather than copying from/to it via In and Out tags) in the AOI may be what you are looking for.