HD6433044 Hitachi Semiconductor, HD6433044 Datasheet - Page 94

• Manufacturer Part Number: HD6433044
• Description: (HD64 Series) Hitachi Single-Chip Microcomputer
• Manufacturer: Hitachi Semiconductor

4.6 Notes on Stack Usage
When accessing word data or longword data, the H8/3048 Series regards the lowest address bit as
0. The stack should always be accessed by word access or longword access, and the value of the
stack pointer (SP, ER7) should always be kept even. Use the following instructions to save
registers:
Use the following instructions to restore registers:
Setting SP to an odd value may lead to a malfunction. Figure 4-7 shows an example of what
happens when the SP value is odd.
SP
Legend
CCR:
PC:
R1L:
SP:
Note: The diagram illustrates modes 3 and 4.
PUSH.W Rn (or MOV.W Rn, @–SP)
PUSH.L ERn (or MOV.L ERn, @–SP)
POP.W Rn
POP.L ERn
Condition code register
Program counter
General register R1L
Stack pointer
SP set to H'FFFEFF
TRAPA instruction executed
(or MOV.W @SP+, Rn)
(or MOV.L @SP+, ERn)
Figure 4-7 Operation when SP Value is Odd
SP
Data saved above SP
CCR
PC
80
MOV. B R1L, @-ER7
SP
CCR contents lost
R1L
PC
H'FFFEFA
H'FFFEFB
H'FFFEFC
H'FFFEFD
H'FFFEFF