HD6432138SW datasheet(154/1061 Pages) RENESAS

154 / 1061 page

Section 4 Exception Handling

Rev. 4.00 Jun 06, 2006 page 100 of 1004

REJ09B0301-0400

4.6

Notes on Use of the Stack

When accessing word data or longword data, the H8S/2138 Group or H8S/2134 Group chip

assumes that the lowest address bit is 0. The stack should always be accessed by word transfer

instruction or longword transfer instruction, and the value of the stack pointer (SP: ER7) should

always be kept even. Use the following instructions to save registers:

PUSH.W

(or MOV.W Rn, @-SP)

PUSH.L

ERn

(or MOV.L ERn, @-SP)

Use the following instructions to restore registers:

POP.W

(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.

Legend:

CCR: Condition-code register

PC:

Program counter

R1L: General register R1L

SP:

Stack pointer

Note: This diagram illustrates an example in which the interrupt control mode is 0, in advanced

mode.

CCR

R1L

H'FFEFFA

H'FFEFFB

H'FFEFFC

H'FFEFFD

H'FFEFFF

MOV.B R1L, @–ER7

SP set to H'FFFEFF

TRAP instruction executed

Data saved above SP

Contents of CCR lost

Figure 4.6 Operation When SP Value Is Odd

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