Fujitsu MB90460 Series Hardware Manual page 65

CHAPTER 3 CPU
PUSHW A with the S flag set to "0"
⇒
Before execution
⇒
After execution
PUSHW A with the S flag set to "1"
⇒
Before execution
⇒
After execution
Notes:
• To set a value for the stack pointer, generally use an even-numbered address.
numbered address is used, a word access is split into two parts, lowering efficiency.
• The initial values of the USP register and SSP register after a reset are undefined.
■ System Stack Pointer (SSP)
To use the system stack pointer (SSP), set the S flag in the condition code register (CCR) of the processor
status (PS) to "1". The upper 8 bits of the address that will be used for the stack operation are indicated by
the system stack bank register (SSB).
■ User Stack Pointer (USP)
To use the user stack pointer (USP), set the S flag in the condition code register (CCR) of the processor
status (PS) to "0". The upper 8 bits of the address that will be used for the stack operation are indicated by
the user stack bank register (USB).
46
Figure 3.7-7 Stack Operation Instruction and Dtack Pointer
AL A624 USB C6
H
S flag 0 SSB 56
AL A624 USB C6
H
S flag 0 SSB 56
AL A624 USB C6
H
S flag 1 SSB 56
AL A624 USB C6
H
S flag 1 SSB 56
USP F328
H H
SSP 1234
H H
⇐
USP F326
H H
SSP 1234
H H
USP F328
H H
SSP 1234
H H
USP F328
H H
⇐
SSP 1232
H H
MSB
XX
C6F326
H
H
User stack is used
because S flag is "0"
A6
C6F326
H
H
MSB
XX
561232
H
H
A6
561232
H
H
System stack is used
because S flag is "1"
LSB
XX
H
24
H
LSB
XX
H
24
H
If an odd-