Usage Note - Renesas H8S/2100 Series Hardware Manual

Section 4 Exception Handling
4.8

Usage Note

When accessing word data or longword data, this LSI assumes that the lowest address bit is 0. The
stack should always be accessed in words or longwords, and the value of the stack pointer (SP:
ER7) should always be kept even.
Use the following instructions to save registers:
PUSH.W Rn
PUSH.L ERn
Use the following instructions to restore registers:
POP.W Rn
POP.L ERn
Setting SP to an odd value may lead to a malfunction. Figure 4.3 shows an example of what
occurs when the SP value is odd.
SP
SP set to H'FFEFFF
[Legend]
CCR: Condition code register
PC: Program counter
R1L: General register R1L
SP: Stack pointer
Note: This diagram illustrates an example in which interrupt control mode is 0 in advanced mode.
Rev. 1.00 Apr. 28, 2008 Page 84 of 994
REJ09B0452-0100
(or
MOV.W Rn, @-SP
(or
MOV.L ERn, @-SP
(or
MOV.W @SP+, Rn
(or
MOV.L @SP+, ERn
CCR
SP
TRAPA instruction executed
Data saved above SP
Figure 4.3 Operation when SP Value Is Odd
)
)
)
)
SP
PC
MOV.B R1L, @-ER7
Contents of CCR lost
R1L H'FFEFFA
H'FFEFFB
H'FFEFFC
PC H'FFEFFD
H'FFEFFF