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C-49
REGISTERS
SP
SP
Address:
Reset State:
18H
XXXXH
The system’s stack pointer (SP) can point anywhere in internal or external memory; 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 0
Stack Pointer
Bit
Number
Function
15:0 Stack Pointer
This register makes up the system’s stack pointer.