read_source_data ERROR

Hello,

I'm a beginner in tcl programming.

I try to use In System Signal Source & Probe (ISSP) by a tcl sript.

At first, I start the ISSP by the command start_insystem_source_probe then I ask the list of available Sources and Probe. It works fine.

But when I want to read the value by the command "exec quartus_stp --tcl_eval read_probe_data -instance_index 0" I have a ERROR message which is ERROR The ISSP instance was not started. THis command cannot be used unless the ISSP trasaction is started.

I don't understand why because the ISSP has been préviously started.

Maybe someone could help me.

Thanks

Pierre