h8s-2646 Renesas Electronics Corporation., h8s-2646 Datasheet - Page 123

• Manufacturer Part Number: h8s-2646
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

4.7
When accessing word data or longword data, the H8S/2646 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:
Use the following instructions to restore registers:
Setting SP to an odd value may lead to a malfunction. Figure 4.6 shows an example of what
happens when the SP value is odd.
Legend:
CCR: Condition code register
PC:
R1L: General register R1L
SP:
Note: This diagram illustrates an example in which the interrupt control mode is 0,
PUSH.W
PUSH.L
POP.W
POP.L
Notes on Use of the Stack
Stack pointer
Program counter
SP
in advanced mode.
SP set to H'FFFEFF
Rn
ERn
Rn
ERn
TRAPA instruction executed
Figure 4.6 Operation when SP Value is Odd
(or MOV.W Rn, @-SP)
(or MOV.L ERn, @-SP)
(or MOV.W @SP+, Rn)
(or MOV.L @SP+, ERn)
SP
Data saved above SP
CCR
PC
MOV.B R1L, @–ER7
Rev. 5.00 Sep 22, 2005 page 97 of 1136
SP
Contents of CCR lost
Section 4 Exception Handling
R1L
PC
REJ09B0257-0500
H'FFFEFA
H'FFFEFB
H'FFFEFC
H'FFFEFD
H'FFFEFF