RL78/G15 CHAPTER 3 CPU ARCHITECTURE
R01UH0959EJ0110 Rev.1.10 Page 67 of 765
Mar 7, 2023
(3) Stack pointer (SP)
This is a 16-bit register to hold the start address of the memory stack area. Only the internal RAM area can be set as the
stack area.
Figure 3-6. Format of Stack Pointer
Symbol 15 0
SP SP15 SP14 SP13 SP12 SP11 SP10 SP9 SP8 SP7 SP6 SP5 SP4 SP3 SP2 SP1 0
In stack addressing through a stack pointer, the SP is decremented ahead of write (save) to the stack memory and is
incremented after read (restore) from the stack memory.
Caution 1. Since reset signal generation makes the SP contents undefined, be sure to initialize the SP before
using the stack.
Caution 2. It is prohibited to use the general-purpose register (FFEE0H to FFEFFH) space for fetching
instructions or a stack area.
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