H8SLASH3003 datasheet(90/715 Pages) RENESAS

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4.6 Notes on Stack Usage

When accessing word data or longword data, the H8/3003 regards the lowest address bit as 0. The

stack should always be accessed by word access or longword access, and the value of the stack

pointer (SP, ER7) should always be kept even. Use the following instructions to save registers:

PUSH.W Rn (or MOV.W Rn, @–SP)

PUSH.L ERn (or MOV.L ERn, @–SP)

Use the following instructions to restore registers:

POP.W Rn

(or MOV.W @SP+, Rn)

POP.L ERn

(or MOV.L @SP+, ERn)

Setting SP to an odd value may lead to a malfunction. Figure 4-6 shows an example of what

happens when the SP value is odd.

Figure 4-6 Operation when SP Value is Odd

TRAPA instruction executed

CCR

Legend

CCR:

PC:

R1L:

SP:

RIL

MOV. B RIL, @-ER7

SP set to H'FFFEFF

Data saved above SP

CCR contents lost

Condition code register

Program counter

General register R1L

Stack pointer

Note: The diagram illustrates modes 3 and 4.

H'FFFEFA

H'FFFEFB

H'FFFEFC

H'FFFEFD

H'FFFEFF

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