Fujitsu MB90895 Series Hardware Manual page 56

CHAPTER 3 CPU
Figure 3.2-8 "Stack Operation Instructions and Stack Pointers" shows an example of the stack operation
using the system stack.
PUSHW A when S flag is "0"
Before
execution
S flag
After
execution
S flag
PUSHW A when S flag is "1"
Before
execution
S flag
After
execution
S flag
X: Undefined
MSB: Most significant bit
LSB: Least significant bit
Notes: • Use even addresses for setting value to the stack pointer. Setting an odd address divides
the word access into two accesses, decreasing the efficiency.
• The reset values of the USP and SSP registers are undefined.
I System stack pointer (SSP)
When using the system stack pointer (SSP), the stack flag (CCR: S) is set to "1". The higher 8 bits of the
address used in processing the stack are set by the system stack bank register (SSB).
I User stack pointer (USP)
When using the user stack pointer (USP), the stack flag (CCR: S) is set to"0". The higher 8 bits of the
address used in processing the stack are set by the user stack bank register (USB).
38
Figure 3.2-8 Stack Operation Instructions and Stack Pointers
AL USB
A624 C6
H H
0 56
SSB
H
AL USB
A624 C6
H H
0 56
SSB
H
AL USB
A624 C6
H H
56
1 SSB
H
AL USB
A624 C6
H H
56
1 SSB
H
MSB
USP
F328 C6F327
H H
1234
SSP
H
Because S flug = "0",
USP
F326
H
use the user stack pointer.
1234
SSP
H
C6F327
H
MSB
USP
F328 561233
H
H
1234
SSP
H
USP
F328 561233
H H
Because S flug = "1",
1232
SSP
H
use the system stack pointer.
LSB
XX XX C6F326
H
H H
A6 24 C6F326
H H
H
LSB
XX XX 561232
H
H H
561232
A6 24
H
H H