UPD78F9418AGK-9EU Renesas Electronics America, UPD78F9418AGK-9EU Datasheet - Page 58

• Manufacturer Part Number: UPD78F9418AGK-9EU
• Manufacturer: Renesas Electronics America

Specifications of UPD78F9418AGK-9EU

• Lead Free Status / Rohs Status: Supplier Unconfirmed

56
(3)
SP
SP
SP
Stack pointer (SP)
This is a 16-bit register used to hold the start address of the memory stack area. Only the internal high-
speed RAM area can be set as the stack area.
The SP is decremented ahead of write (save) to the stack memory and is incremented after read (restore)
from the stack memory.
Each stack operation saves/restores data as shown in Figures 3-12 and 3-13.
Caution Since RESET input makes the SP contents undefined, be sure to initialize the SP before
SP _ 2
SP _ 2
SP _ 1
SP + 1
SP + 2
SP15
15
SP
SP
SP14
instruction execution.
SP13 SP12 SP11 SP10
Lower
register pairs
Higher
register pairs
Lower
register pairs
Higher
register pairs
POP rp
instruction
PUSH rp
instruction
Figure 3-13. Data Restored from Stack Memory
Figure 3-12. Data Saved to Stack Memory
Figure 3-11. Stack Pointer Configuration
CHAPTER 3 CPU ARCHITECTURE
SP
SP
User’s Manual U13952EJ3V1UD
SP _ 2
SP _ 2
SP _ 1
SP + 1
SP + 2
SP9
SP
SP
SP8
RET instruction
PC15 to PC8
PC15 to PC8
CALL, CALLT
instructions
PC7 to PC0
PC7 to PC0
SP7
SP6
SP5
SP
SP
SP4
SP _ 3
SP _ 3
SP _ 2
SP _ 1
SP + 1
SP + 2
SP + 3
SP
SP
SP3
SP2
RETI instruction
PC15 to PC8
PC15 to PC8
PC7 to PC0
PC7 to PC0
Interrupt
SP1
PSW
PSW
SP0
0