What is STR?

Hi,

In "7.6.1 Example1" and "7.6.2 Example2" of TRM (SPNU499),
"(e) Resume the Test if required using Program Control register (offset = 0x16C) STR = 2." is described.
However, I can't find STR means.
Could you explain it and how to resume PBIST?

Thanks

Nomoto