HD64F3039F18 Datasheet, PDF (106/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 4 Exception Handling
4.6 Notes on Stack Usage
When accessing word data or longword data, the H8/3039 Group 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 4.5 shows an example of what
happens when the SP value is odd.
CCR
SP
R1L
H'FFEFA
SP
H'FFEFB
PC
PC
H'FFEFC
H'FFEFD
H'FFEFF
SP
TRAPA instruction executed
MOV. B R1L, @-ER7
SP set to H'FFEFF
Data saved above SP
CCR contents lost
Legend:
CCR: Condition code register
PC: Program counter
R1L: General register R1L
SP: Stack pointer
Note: The diagram illustrates modes 1, 3, and 5.
Figure 4.5 Operation when SP Value is Odd
Rev.3.00 Mar. 26, 2007 Page 82 of 682
REJ09B0353-0300