Datasheet

Section 4 Exception Handling
Rev.7.00 Dec. 24, 2008 Page 90 of 698
REJ09B0074-0700
4.8 Notes on Use of the Stack
When accessing word data or longword data, this LSI 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 4.4 shows an example of what
happens when the SP value is odd.
SP
CCR:
PC:
R1L:
SP:
Condition code register
Program counter
General register R1L
Stack pointer
CCR
SP
SP
R1L
H'FFFEFA
H'FFFEFB
H'FFFEFC
H'FFFEFD
H'FFFEFE
H'FFFEFF
PC PC
TRAPA instruction executedSP set to H'FFFEFF
Data saved above SP
MOV.B R1L, @-ER7 executed
Contents of CCR lost
Address
Legend:
Note: This diagram illustrates an example in which the interrupt control mode is 0, in advanced mode.
Figure 4.4 Operation when SP Value Is Odd