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; * The definition of the "register test" tasks, as described at the top of
; * main.c

        .include data_model.h

        .global vTaskIncrementTick
        .global vTaskSwitchContext
        .global vPortSetupTimerInterrupt
        .global pxCurrentTCB
        .global usCriticalNesting

        .def vPortPreemptiveTickISR
        .def vPortCooperativeTickISR
        .def vPortYield
        .def xPortStartScheduler

;-----------------------------------------------------------

portSAVE_CONTEXT .macro

        ;Save the remaining registers.
        pushm_x #12, r15
        mov.w   &usCriticalNesting, r14
        push_x r14
        mov_x   &pxCurrentTCB, r12
        mov_x   sp, 0( r12 )
        .endm
;-----------------------------------------------------------
                
portRESTORE_CONTEXT .macro

        mov_x   &pxCurrentTCB, r12
        mov_x   @r12, sp
        pop_x   r15
        mov.w   r15, &usCriticalNesting
        popm_x  #12, r15
                
        ;The last thing on the stack will be the status register.
    ;Ensure the power down bits are clear ready for the next
    ;time this power down register is popped from the stack.
        bic.w   #0xf0, 0( sp )
                
        pop.w   sr
        ret_x
        .endm
;-----------------------------------------------------------

;*
;* The RTOS tick ISR.
;*
;* If the cooperative scheduler is in use this simply increments the tick
;* count.
;*
;* If the preemptive scheduler is in use a context switch can also occur.
;*/
        
        .text
        .align 2
        
vPortPreemptiveTickISR: .asmfunc
        
        ; The sr is not saved in portSAVE_CONTEXT() because vPortYield() needs
        ;to save it manually before it gets modified (interrupts get disabled).
        push.w sr
        portSAVE_CONTEXT
                                
        call_x  #vTaskIncrementTick
        call_x  #vTaskSwitchContext
                
        portRESTORE_CONTEXT
        .endasmfunc
;-----------------------------------------------------------

        .align 2
        
vPortCooperativeTickISR: .asmfunc
        
        ; The sr is not saved in portSAVE_CONTEXT() because vPortYield() needs
        ;to save it manually before it gets modified (interrupts get disabled).
        push.w sr
        portSAVE_CONTEXT
                                
        call_x  #vTaskIncrementTick
                
        portRESTORE_CONTEXT
        
        .endasmfunc
;-----------------------------------------------------------

;
; Manual context switch called by the portYIELD() macro.
;

        .align 2

vPortYield: .asmfunc

        ; The sr needs saving before it is modified.
        push.w  sr
        
        ; Now the SR is stacked we can disable interrupts.
        dint    
        nop
                                
        ; Save the context of the current task.
        portSAVE_CONTEXT                        

        ; Select the next task to run.
        call_x  #vTaskSwitchContext             

        ; Restore the context of the new task.
        portRESTORE_CONTEXT
        .endasmfunc
;-----------------------------------------------------------


;
; Start off the scheduler by initialising the RTOS tick timer, then restoring
; the context of the first task.
;

        .align 2
        
xPortStartScheduler: .asmfunc

        ; Setup the hardware to generate the tick.  Interrupts are disabled
        ; when this function is called.
        call_x  #vPortSetupTimerInterrupt

        ; Restore the context of the first task that is going to run.
        portRESTORE_CONTEXT
        .endasmfunc
;-----------------------------------------------------------
                
        .end