signal function have no infinite loop.it will exit after the last sentence?
if yes ,why i can't call the signal function twice?
Because the description of a Signal Function specifically tells you not to:
"Signal functions can be invoked only once. If the function is invoked twice, then a warning is displayed."
www.keil.com/.../uv4_df_signalfunctions.htm
Actually the sentence is slightly mis-leading. Signal functions can run only in one instance is correct. You you cannot execute the same signal function at the same time twice.