Datasheet

Section 4 Exception Handling
Rev.6.00 Sep. 27, 2007 Page 109 of 1268
REJ09B0220-0600
4.7 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 4.5 shows an example of what
happens when the SP value is odd.
SP
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.
SP
SP
CCR
PC
R1L
PC
H'FFFEFA
H'FFFEFB
H'FFFEFC
H'FFFEFD
MOV.B R1L, @–ER7
SP set to H'FFFEFF
TRAP instruction executed
Data saved above SP Contents of CCR lost
Figure 4.5 Operation when SP Value is Odd