Intel 8XC196NT User Manual page 548

SP
The system's stack pointer (SP) can point anywhere in an internal or external memory page; it must
be word aligned and must always be initialized before use. The stack pointer is decremented before a
PUSH and incremented after a POP, so the stack pointer should be initialized to two bytes (in 64-
Kbyte mode) or four bytes (in 1-Mbyte mode) above the highest stack location. If stack operations are
not being performed, locations 18H and 19H may be used as standard registers.
15
7
Bit
Number
15:0 Stack Pointer
This register makes up the system's stack pointer.
Stack Pointer (high byte)
Stack Pointer (low byte)
Function
REGISTERS
Address: 18H
Reset State: XXXXH
8
0
C-53
SP