Fujitsu MB90895 Series Hardware Manual page 57

I Stack Area
G
Securing stack area
The stack area is used to save and return the program counter (PC) at execution of the interrupt processing,
subroutine call instruction (CALL) and vector call instruction (CALLV). It is also used to save and return
temporary registers using the PUSHW and POP
The stack area is secured with the data area in RAM.
The stack area is as shown below:
Vector table
(reset, interrupt
vector call instruction)
*: The capacity of the internal ROM depends on the product.
Notes: • As a general rule, even addresses should be set in the stack pointers (SSP and USP).
• The system stack area, user stack area, and data area should not overlap.
G
System stack area and user stack area
The system stack area is used for interrupt processing. When an interrupt occurs, even though the user stack
area is being used, it is forced to be switched to the system stack area. Therefore, in systems mainly using
the user stack area also, the system stack area must be set correctly.
In particular, only the system stack area should be used unless it is necessary to divide the stack space.
Figure 3.2-9 Stack Area
000000
H
0000C0
H
000100
H
000180
H
Stack area
000380
H
000900
H
*
FF0000
H
FFFC00
H
FFFFFF
H
I/O area
General purpose
register
bank area
Internal RAM area
ROM area
CHAPTER 3 CPU
39