HD64F2149 Datasheet, PDF (130/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

4.6 Notes on Use of the Stack
When accessing word data or longword data, the 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 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.
CCR
SP
SP
PC
R1L
H'FFFEFA
H'FFFEFB
PC
H'FFFEFC
H'FFFEFD
SP
H'FFFEFF
TRAP instruction executed MOV.B R1L, @–ER7
SP set to H'FFFEFF Data saved above SP Contents of CCR lost
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.
Figure 4.6 Operation when SP Value is Odd
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