# \[BUG\] v8.1.5 AB Logix driver - Tags that are written and reset by PLC in 1 scan remain **URL:** \ **Category:** Ignition\ **Tags:** ignition81\ **Created:** [June 3, 2021, 2:19am UTC](https://forum.inductiveautomation.com/t/bug-v8-1-5-ab-logix-driver-tags-that-are-written-and-reset-by-plc-in-1-scan-remain/47378 "2021-06-03T02:19:07Z")\ **Posts on this page:** 1\ **Showing post:** 12
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [August 2, 2022, 11:59pm UTC](https://forum.inductiveautomation.com/t/bug-v8-1-5-ab-logix-driver-tags-that-are-written-and-reset-by-plc-in-1-scan-remain/47378/12 "2022-08-02T23:59:24Z")
Ah-ha, I found my original post where I described the race condition, and in that version it was explicitly about read-after-write: > If Ignition isn’t the only thing that will write to a given tag then I’d recommend not using the “Read after write” setting because there’s a somewhat dangerous race condition and it’s more likely to occur when using slow scan classes / subscriptions. > > Imagine, if you will, a boolean tag in a 30 second scan class. > > 1. driver polls value=`false`, next poll in 30s > 2. user writes value=`true` to tag, read-after-write confirms value=`true`, ignition tag now set to true > 3. some seconds later, before the next poll, an external source (script, PLC logic, whatever) sets the value to `false` again > 4. driver eventually polls again, reads value=`false`, no change since last poll, so no data change is sent to client > > The tag is now false in the PLC but true in Ignition. from [Indirect Tag Delay - #9 by Kevin.Herron](https://forum.inductiveautomation.com/t/indirect-tag-delay/28734/9) I somehow telephoned my own race condition description into something inaccurate since then. --- _[View the full topic](https://forum.inductiveautomation.com/t/bug-v8-1-5-ab-logix-driver-tags-that-are-written-and-reset-by-plc-in-1-scan-remain/47378)._