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C-41
REGISTERS
SP
SP
Address:
Reset State:
18H
XXXXH
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 8
Stack Pointer (high byte)
7 0
Stack Pointer (low byte)
Bit
Number
Function
15:0 Stack Pointer
This register makes up the system’s stack pointer.