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CHAPTER 3 REGISTER DESCRIPTIONS
Figure 3.3-13 Example of Stack Pointer Operation in Execution of Instruction "ST R13", "@-R15"
Before execution of ST R13,@-R15
SSP
12345678
USP
76543210
R13
17263540
S
CCR
1
■ Stack Pointer Configuration
Figure 3.3-14shows the bit configuration of the stack pointer.
Bit no.
SSP
USP
■ Functions of the System Stack Pointer and User Stack Pointer
●
Automatic increment/decrement of stack pointer
The stack pointer uses automatic pre-decrement/post-increment counting.
●
Stack Pointer Initial Value
The "SSP" has the initial value "00000000
■ Recovery from EIT handler
When RETI instruction is used for recovery from EIT handler, it is required to set the "S" flag to "0" and
select the system stack. For further details, see "4.2 Basic Operations in "EIT" Processing
from EIT handler".
28
when "S" Flag = "1"
Memory space
00000000
H
????????
H
????????
H
H
FFFFFFFF
H
Figure 3.3-14 Bit Configuration of the Stack Pointers
31
After execution of ST R13,@-R15
SSP
12345678
USP
7654320C
R13
17263540
S
CCR
1
". The "USP" initial value is undefined.
H
Memory space
00000000
H
17263540
H
H
H
H
FFFFFFFF
H
00
■
Recovery
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