# S7-1500 driver issue

**URL:** <https://forum.inductiveautomation.com/t/s7-1500-driver-issue/57460>\
**Category:** Ignition\
**Created:** [March 22, 2022, 3:02pm UTC](https://forum.inductiveautomation.com/t/s7-1500-driver-issue/57460 "2022-03-22T15:02:20Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![pgmo](https://avatars.discourse-cdn.com/v4/letter/p/d07c76/32.png) [@pgmo](https://forum.inductiveautomation.com/u/pgmo)\
**Post date:** [March 22, 2022, 3:02pm UTC](https://forum.inductiveautomation.com/t/s7-1500-driver-issue/57460/1 "2022-03-22T15:02:20Z")

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I’m using Ignition version 8.1.13 on a S7-1500 PLC. One of the PLC’s datablocks have up to 1200 variables, first half DINT, second half REAL. In the REAL part of the datablock I’m experiencing the following issue: suppose you have **var1** at address offset 460 and **var2** at address offset 464. From time to time **var2** freezes and get no more updates, while TIA Portal (Siemens PLC software) shows **var2** updates correctly. When that happens, in order to get **var2** updates I have to issue the _restart command_ on the variable. No errors are shown in Ignition logs, nor in the variable diagnostic.  
I tried a workaround, creating a separte S7-1500 device, just to read that only variable, but with no sucess.

Any suggestion?

Tanks in advance, regards

**UPDATE**  
Since **VAR2** is the pressure in mbar, whereas **VAR1** is the same pressure in Pascal, we decided to change **VAR2** to an _expression tag_, i.e. **VAR1/100**. The same behaviour is affecting **VAR2** too, even if it is an _expression tag_ now. **VAR1** is something like 1.23E-4 and **VAR2** should be something like 1.23E-6. Question: has Ignition any known issues in handling so small **float** values?