Datasheet

Rev.6.00 Oct.28.2004 page 79 of 1016
REJ09B0138-0600H
4.7 Notes on Use of the Stack
When accessing word data or longword data, the H8S/2357 Group 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:
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
H'FFFEFF
MOV.B R1L, @–ER7
SP set to H'FFFEFF
TRAPA instruction executed
Data saved above SP Contents of CCR lost
CCR: Condition code register
PC: Program counter
R1L: General register R1L
SP: Stack pointer
Figure 4-5 Operation when SP Value is Odd