*** YOU NEED TO REGISTER ON THE FORUM BEFORE YOU CAN ACCESS THE DOWNLOAD LINK ***
INSTALLATION INSTRUCTIONS
http://www.xperiablog.net/2015/03/17/guide-to-installing-xperia-lollipop-using-xperifirm-and-flashtool/
- Open link above and skip to the section entitled “FlashTool steps”.
- As you have already downloaded the FTF firmware file, skip to the section where you need to “Flash device”.
XPERIA FIRMWARE DETAILS
This is official stock Sony Xperia firmware.
Model: Sony Ericsson Xperia PLAY (R800at)
Firmware version: 3.0.1.B.0.285_R40C
Region: US (AT&T) [1248-6414]
Android version: 2.3.3

Xperia PLAY_R800at_3.0.1.B.0.285_US_AT&T 2.3.3
Sony Ericsson Xperia PLAY (R800at) Android 2.3.3 firmware - AT&T US