D78F9189CT データシートの表示（PDF） - NEC => Renesas Technology

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D78F9189CT

UPD78F9189CT, D78F9189CT / 8-Bit Single-chip Microcontroller

NEC => Renesas Technology 

CHAPTER 3 CPU ARCHITECTURE

(3) Stack pointer (SP)

This is a 16-bit register to hold the start address of the memory stack area. Only the internal high-speed

RAM area can be set as the stack area.

Figure 3-9. Stack Pointer Configuration

15

0

SP SP15 SP14 SP13 SP12 SP11 SP10 SP9 SP8 SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0

The SP is decremented ahead of writing (saving) to the stack memory and is incremented after reading

(restoring) from the stack memory.

Each stack operation saves/restores data as shown in Figures 3-10 and 3-11.

Caution Since RESET input makes SP contents undefined, be sure to initialize the SP before

instruction execution.

Figure 3-10. Data to be Saved to Stack Memory

SP SP _ 2

SP _ 2

SP _ 1

SP

PUSH rp

instruction

Register pair

lower

Register pair

higher

SP SP _ 2

SP _ 2

SP _ 1

SP

CALL, CALLT

instructions

SP SP _ 3

SP _ 3

PC7 to PC0

SP _ 2

PC15 to PC8

SP _ 1

SP

Interrupt

PC7 to PC0

PC15 to PC8

PSW

Figure 3-11. Data to be Restored from Stack Memory

POP rp

instruction

RET instruction

RETI instruction

SP

SP + 1

SP SP + 2

Register pair

lower

Register pair

higher

SP

SP + 1

SP SP + 2

PC7 to PC0

PC15 to PC8

SP

SP + 1

SP + 2

SP SP + 3

PC7 to PC0

PC15 to PC8

PSW

User’s Manual 2nd edition

37

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