RS08KA2 PROMO Freescale Semiconductor, RS08KA2 PROMO Datasheet - Page 18

• Manufacturer Part Number: RS08KA2 PROMO
• Description: DEMO KIT, SILICON BUNDLE, RS08KA2
• Manufacturer: Freescale Semiconductor

Specifications of RS08KA2 PROMO

• Kit Contents: DEMO9RS08KA2 Board, USB Cable, Quick Start Guide, User Manual, Packing List
• Svhc: No SVHC (15-Dec-2010)
• Development Tool Type: Demonstration Kit
• Kit Features: RS08KA2 Microcontroller,
• Silicon Manufacturer: Freescale
• Core Architecture: RS08
• Core Sub-architecture: RS08
• Silicon Core Number: MC9RS08
• Silicon Family Name: RS08KA
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Introduction to RS08
1.7
The RS08 platform provides only a single level of hardware stacking. When the instruction, JSR or BSR,
is executed, current program counter (PC) value is uploaded to the shadow program counter (SPC) register
before the PC is modified with a new location. In the case when the program encounters the instruction
RTS, the saved PC value is restored from the SPC register. Program execution resumes at the address that
was just restored from SPC register.
Single level of subroutine call may not be sufficient for some applications, multi-level software stacking
can be emulated with the help of SHA/SLA instructions. These instructions exchange the high byte and
the low byte of SPC register with accumulator A respectively. Software stacking can be implemented that
place the SPC content for each level of subroutine call in RAM.
The following code shows how software stacking can be implemented in macro format. In this example,
location $00 is arbitrarily chosen for the stack pointer (STACKPTR) variable and the stack content is
placed from address $4F downwards. The code shown provides no stack overflow checking.
SPInit
FLASHSTART
RESETSP: MACRO
PSH_SPC: MACRO
PUL_SPC: MACRO
STACKPTR
18
Subroutine Call
mov
ENDM
; NOTE: Destructive to X content
ldx
sha
sta
sha
decx
sla
sta
sla
decx
stx
ENDM
; NOTE: Destructive to X content
ldx
incx
sla
lda
sla
incx
sha
lda
sha
stx
ENDM
org
org
equ
equ
#SPInit, STACKPTR
STACKPTR
,X
,X
STACKPTR
STACKPTR
,X
,X
STACKPTR
TINY_RAM
ds.b
FLASHSTART
$4F
$3800
1
Getting Started with RS08, Rev. 1
; Stack block allocation
; For MC9RS08KA2
; Init Stack pointer
; 20 CPU cycles, 14 bytes code
; Load Stack pointer
; Swap SPC high byte
; Push high byte to stack
; Resume A content
; update stack pointer
; Swap SPC low byte
; Push low byte to stack
; Resume A content
; update stack pointer
; Save stack pointer
; 22 CPU cycles, 14 byte code
; Load Stack pointer
; Update stack pointer
; Swap SPC low byte
; Pull low byte
; Resume A and SPCL content
; Update stack pointer
; Swap SPC high byte
; Pull high byte
; Resume A and SPCH content
; Save stack pointer
; Stack pointer location
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