Toshiba T2N - Manual (Page 157)

2. User Program Configuration
144 PROSEC T2N
2.3.2
Sub-Program
Sub-program #1 can be created which is executed only once at the head
of the first scan when the T2N starts to RUN.
Therefore, when used for the initial value setting of registers, in order
that it may not be programmed in the main program, it also has the
effect of reducing the total scan time.
The sub-program #1 must be ended by an END instruction.