IBM 5170 Technical Reference page 349

Restore State
I
escape 101
I
mod 100
rim
FINCSTP
=
Increment Stack Pointer
Increment Stack Pointer
1 escape 001
1 11110111
FDECSTP
=
Decrement Stack Pointer
Decrement Stack Pointer
1
escape 001
111110110
FFREE
=
Free ST(i)
Free ST(j)
I
escape 101
1
11000ST(i)
FNOP
=
No Operation
No Operation
I
escape 001 11010000
Instruction Set 6-31