Siemens Simatic S5-95U-Stopped Error

Dear All,,
We have a Siemens Simatic S5-95U and there is stopped red LED active
Tried resetting the PLC,switching the Run/Stop toggle push button but PLC cannot go back to RUN mode.
What are the possible causes/errors to this problem
And what is the name of the PLC programming software for Simatic S5 and where can i download?
Need some help

Thank you
I worked on S5 over 20years ago and they were discontinued then !
The Software was STEP5 which ran on CPM and later DOS3.0.

Have you got the application program to download ?

The controller could be completely broken or could be flat battery
(I believe there was EPROM versions where battery back-up wasn't required)

If you do manage to find replacement CPU and STEP5 software, the programming
lead is a problem. The CPU requires 20ma serial data - even in those days
PC's were RS232 serial so you would need a RS232/20ma converter.
Thinking about it, try sourcing a 2nd hand vintage Siemens portable PC (couldn't
call them laptops) of the day. They had the German keyboards and built in
20ma socket.
Have a look on the internet for free downloads of the STEP5 software. Alternatively look at IBH Softec. They will sell you a program (not Siemens original) but it is easier to use. It might be suitable for early versions of Windows (maybe XP) which the original STEP5 was not. For the original stuff you would need a computer running DOS. I downloaded something I was going to send you but it was too big for this website to accept (24+MB) I haven't tested it anyway. Like the man says above, you need a special cable too. Let us all know how you get on. Good luck.