HD64F3028F25 Datasheet, PDF (111/925 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

4.6 Notes on Stack Usage
When accessing word data or longword data, the H8/3028 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 4.7 shows an example of what
happens when the SP value is odd.
CCR
SP
SP
PC
R1L
H'FFFEFA
H'FFFEFB
PC
H'FFFEFC
H'FFFEFD
H'FFFEFF
SP
TRAPA instruction executed
MOV. B R1L, @-ER7
SP set to H'FFFEFF
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 3 and 4.
Figure 4.7 Operation when SP Value is Odd
Rev. 2.00, 09/03, page 79 of 890