S3F9488 datasheet(26/49 Pages) SAMSUNG

26 / 49 page

S3C9484/C9488/F9488

ADDRESS SPACES

2-7

SYSTEM STACK

S3F9-series microcontrollers use the system stack for subroutine calls and returns and to store data. The PUSH

and POP instructions are used to control system stack operations. The S3C9484/C9488/F9488 architecture

supports stack operations in the internal register file.

Stack Operations

Return addresses for procedure calls and interrupts and data are stored on the stack. The contents of the PC are

saved to stack by a CALL instruction and restored by the RET instruction. When an interrupt occurs, the contents of

the PC and the FLAGS registers are pushed to the stack. The IRET instruction then pops these values back to their

original locations. The stack address always decrements before a push operation and increments after a pop

operation. The stack pointer (SP) always points to the stack frame stored on the top of the stack, as shown in

Figure 2-5.

Stack contents

after a call

instruction

Stack contents

after an

interrupt

Top of

stack

Flags

PCH

PCL

PCH

Top of

stack

Low Address

High Address

Figure 2-5. Stack Operations

Stack Pointer (SP)

the SP value is undetermined.

Because only internal memory space is implemented in the S3C9484/C9488/F9488, the SP must be initialized to an

8-bit value in the range 00H–0C0H.

NOTE

In case a Stack Pointer is initialized to 00H, it is decreased to FFH when stack operation starts. This

means that a Stack Pointer access invalid stack area. We recommend that a stack pointer is initialized to

C0H to set upper address of stack to BFH.

S3F9488 Datasheet(PDF) 26 Page - Samsung semiconductor