H8S2245 datasheet(144/818 Pages) RENESAS

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Section 4 Exception Handling

Rev.3.00 Mar. 26, 2007 Page 102 of 772

REJ09B0355-0300

4.6

Notes on Use of the Stack

When accessing word data or longword data, the H8S/2245 Group 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:

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

in advanced mode.

CCR

R1L

H'FFFEFA

H'FFFEFB

H'FFFEFC

H'FFFEFD

H'FFFEFF

MOV.B R1L, @–ER7

SP set to H'FFFEFF

TRAPA instruction executed

Data saved above SP

Contents of CCR lost

CCR: Condition code register

PC:

Program counter

R1L: General register R1L

SP:

Stack pointer

Figure 4.6 Operation when SP Value is Odd

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