Just joined forum so sorry if this isn't much use to you.
The top unit is actually a re-badged Eurotherm T940.
The software to program both the PAC T2500 and T940 is LINtools provided by Eurotherm. LIN stands for Local Instrument Network.
There is a specific cable required to connect from your computer USB port - it's an ARCNET driver and it's available from Eurotherm.
I'd contact your local Eurotherm representative or contact their UK office on +44 (0)1903 268 500 and ask for the Systems Helpdesk or Technical helpdesk.
Jim