Configure Device to have a single ASCII file that is overwritten every 30 sec

I am trying to write a single data file through Report/Device features.  However, I have not able to configure the device to create a single file and to be overwritten every 30.seconds. Would anyone be able to give me some suggestion?  I am currently running Vijeo Citect 2015.

In citect.ini:  Device.CreateHistoryFiles = 1

In device configuration:  Type:ASCII_DEV;  No. File: 1; Time: ; Period: 00:00:30;