3-202
INSTRUCTION SET REFERENCE
FINCSTP—Increment Stack-Top Pointer
Description
This instruction adds one to the TOP field of the FPU status word (increments the top-of-stack
pointer). If the TOP field contains a 7, it is set to 0. The effect of this instruction is to rotate the
stack by one position. The contents of the FPU data registers and tag register are not affected.
This operation is not equivalent to popping the stack, because the tag for the previous top-of-
stack register is not marked empty.
Operation
IF TOP = 7
THEN TOP
<
0;
ELSE TOP
<
TOP + 1;
FI;
FPU Flags Affected
The C1 flag is set to 0; otherwise, cleared to 0. The C0, C2, and C3 flags are undefined.
Floating-Point Exceptions
None.
Protected Mode Exceptions
#NM
EM or TS in CR0 is set.
Real-Address Mode Exceptions
#NM
EM or TS in CR0 is set.
Virtual-8086 Mode Exceptions
#NM
EM or TS in CR0 is set.
Opcode
Instruction
Description
D9 F7
FINCSTP
Increment the TOP field in the FPU status register
