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/* cpu_asm.s
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*
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* This file contains all assembly code for the MC68020 implementation
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* of RTEMS.
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*
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* COPYRIGHT (c) 1989-1999.
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* On-Line Applications Research Corporation (OAR).
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.OARcorp.com/rtems/license.html.
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*
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* $Id: cpu_asm.S,v 1.2 2001-09-27 11:59:28 chris Exp $
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*/
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#include
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.text
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/* void _CPU_Context_switch( run_context, heir_context )
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*
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* This routine performs a normal non-FP context.
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*/
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.align 4
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.global SYM (_CPU_Context_switch)
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.set RUNCONTEXT_ARG, 4 | save context argument
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.set HEIRCONTEXT_ARG, 8 | restore context argument
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SYM (_CPU_Context_switch):
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moval a7@(RUNCONTEXT_ARG),a0| a0 = running thread context
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movw sr,d1 | d1 = status register
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movml d1-d7/a2-a7,a0@ | save context
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moval a7@(HEIRCONTEXT_ARG),a0| a0 = heir thread context
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restore: movml a0@,d1-d7/a2-a7 | restore context
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movw d1,sr | restore status register
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rts
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/*PAGE
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* void __CPU_Context_save_fp_context( &fp_context_ptr )
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* void __CPU_Context_restore_fp_context( &fp_context_ptr )
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*
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* These routines are used to context switch a MC68881 or MC68882.
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*
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* NOTE: Context save and restore code is based upon the code shown
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* on page 6-38 of the MC68881/68882 Users Manual (rev 1).
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*
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* CPU_FP_CONTEXT_SIZE is higher than expected to account for the
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* -1 pushed at end of this sequence.
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*
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* Neither of these entries is required if we have software FPU
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* emulation. But if we don't have an FPU or emulation, then
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* we need the stub versions of these routines.
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*/
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#if (CPU_SOFTWARE_FP == FALSE)
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.set FPCONTEXT_ARG, 4 | save FP context argument
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.align 4
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.global SYM (_CPU_Context_save_fp)
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SYM (_CPU_Context_save_fp):
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#if ( M68K_HAS_FPU == 1 )
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moval a7@(FPCONTEXT_ARG),a1 | a1 = &ptr to context area
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moval a1@,a0 | a0 = Save context area
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fsave a0@- | save 68881/68882 state frame
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tstb a0@ | check for a null frame
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beq nosv | Yes, skip save of user model
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fmovem fp0-fp7,a0@- | save data registers (fp0-fp7)
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fmovem fpc/fps/fpi,a0@- | and save control registers
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movl #-1,a0@- | place not-null flag on stack
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nosv: movl a0,a1@ | save pointer to saved context
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#endif
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rts
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.align 4
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.global SYM (_CPU_Context_restore_fp)
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SYM (_CPU_Context_restore_fp):
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#if ( M68K_HAS_FPU == 1 )
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moval a7@(FPCONTEXT_ARG),a1 | a1 = &ptr to context area
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moval a1@,a0 | a0 = address of saved context
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tstb a0@ | Null context frame?
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beq norst | Yes, skip fp restore
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addql #4,a0 | throwaway non-null flag
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fmovem a0@+,fpc/fps/fpi | restore control registers
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fmovem a0@+,fp0-fp7 | restore data regs (fp0-fp7)
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norst: frestore a0@+ | restore the fp state frame
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movl a0,a1@ | save pointer to saved context
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#endif
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rts
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#endif
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/*PAGE
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* void _ISR_Handler()
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*
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* This routine provides the RTEMS interrupt management.
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*
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* NOTE:
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* Upon entry, the master stack will contain an interrupt stack frame
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* back to the interrupted thread and the interrupt stack will contain
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* a throwaway interrupt stack frame. If dispatching is enabled, this
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* is the outer most interrupt, and (a context switch is necessary or
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* the current thread has signals), then set up the master stack to
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* transfer control to the interrupt dispatcher.
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*/
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/*
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* With this approach, lower priority interrupts may
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* execute twice if a higher priority interrupt is
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* acknowledged before _Thread_Dispatch_disable is
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* incremented and the higher priority interrupt
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* performs a context switch after executing. The lower
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* priority interrupt will execute (1) at the end of the
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* higher priority interrupt in the new context if
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* permitted by the new interrupt level mask, and (2) when
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* the original context regains the cpu.
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*/
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#if ( M68K_COLDFIRE_ARCH == 1 )
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.set SR_OFFSET, 2 | Status register offset
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.set PC_OFFSET, 4 | Program Counter offset
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.set FVO_OFFSET, 0 | Format/vector offset
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#elif ( M68K_HAS_VBR == 1)
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.set SR_OFFSET, 0 | Status register offset
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.set PC_OFFSET, 2 | Program Counter offset
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.set FVO_OFFSET, 6 | Format/vector offset
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#else
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.set SR_OFFSET, 2 | Status register offset
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.set PC_OFFSET, 4 | Program Counter offset
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.set FVO_OFFSET, 0 | Format/vector offset placed in the stack
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#endif /* M68K_HAS_VBR */
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.set SAVED, 16 | space for saved registers
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.align 4
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.global SYM (_ISR_Handler)
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SYM (_ISR_Handler):
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addql #1,SYM (_Thread_Dispatch_disable_level) | disable multitasking
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#if ( M68K_COLDFIRE_ARCH == 0 )
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moveml d0-d1/a0-a1,a7@- | save d0-d1,a0-a1
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movew a7@(SAVED+FVO_OFFSET),d0 | d0 = F/VO
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andl #0x0fff,d0 | d0 = vector offset in vbr
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#else
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lea a7@(-SAVED),a7
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movm.l d0-d1/a0-a1,a7@ | save d0-d1,a0-a1
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movew a7@(SAVED+FVO_OFFSET),d0 | d0 = F/VO
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andl #0x0ffc,d0 | d0 = vector offset in vbr
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#endif
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#if ( CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 )
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#if ( M68K_COLDFIRE_ARCH == 0 )
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movew sr,d1 | Save status register
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oriw #0x700,sr | Disable interrupts
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#else
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move.l d0,a7@- | Save d0 value
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move.l #0x700,d0 | Load in disable ints value
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move.w sr,d1 | Grab SR
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or.l d1,d0 | Create new SR
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move.w d0,sr | Disable interrupts
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move.l a7@+,d0 | Restore d0 value
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#endif
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tstl SYM (_ISR_Nest_level) | Interrupting an interrupt handler?
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bne 1f | Yes, just skip over stack switch code
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movel SYM(_CPU_Interrupt_stack_high),a0 | End of interrupt stack
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movel a7,a0@- | Save task stack pointer
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movel a0,a7 | Switch to interrupt stack
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1:
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addql #1,SYM(_ISR_Nest_level) | one nest level deeper
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movew d1,sr | Restore status register
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#else
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addql #1,SYM (_ISR_Nest_level) | one nest level deeper
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#endif /* CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 */
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#if ( M68K_HAS_PREINDEXING == 1 )
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movel @( SYM (_ISR_Vector_table),d0:w:1),a0| fetch the ISR
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#else
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movel # SYM (_ISR_Vector_table),a0 | a0 = base of RTEMS table
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addal d0,a0 | a0 = address of vector
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movel (a0),a0 | a0 = address of user routine
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#endif
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lsrl #2,d0 | d0 = vector number
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movel d0,a7@- | push vector number
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jbsr a0@ | invoke the user ISR
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addql #4,a7 | remove vector number
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#if ( CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 )
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#if ( M68K_COLDFIRE_ARCH == 0 )
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movew sr,d0 | Save status register
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oriw #0x700,sr | Disable interrupts
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#else
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move.l #0x700,d1 | Load in disable int value
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move.w sr,d0 | Grab SR
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or.l d0,d1 | Create new SR
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move.w d1,sr | Load to disable interrupts
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#endif
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subql #1,SYM(_ISR_Nest_level) | Reduce interrupt-nesting count
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bne 1f | Skip if return to interrupt
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movel (a7),a7 | Restore task stack pointer
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1:
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movew d0,sr | Restore status register
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#else
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subql #1,SYM (_ISR_Nest_level) | one less nest level
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#endif /* CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 */
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subql #1,SYM (_Thread_Dispatch_disable_level)
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| unnest multitasking
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bne exit | If dispatch disabled, exit
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#if ( M68K_HAS_SEPARATE_STACKS == 1 )
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movew #0xf000,d0 | isolate format nibble
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andw a7@(SAVED+FVO_OFFSET),d0 | get F/VO
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cmpiw #0x1000,d0 | is it a throwaway isf?
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bne exit | NOT outer level, so branch
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#endif
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tstl SYM (_Context_Switch_necessary)
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| Is thread switch necessary?
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bne bframe | Yes, invoke dispatcher
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tstl SYM (_ISR_Signals_to_thread_executing)
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| signals sent to Run_thread
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| while in interrupt handler?
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beq exit | No, then exit
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bframe: clrl SYM (_ISR_Signals_to_thread_executing)
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| If sent, will be processed
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#if ( M68K_HAS_SEPARATE_STACKS == 1 )
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movec msp,a0 | a0 = master stack pointer
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movew #0,a0@- | push format word
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movel #SYM(_ISR_Dispatch),a0@- | push return addr
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movew a0@(6),a0@- | push saved sr
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movec a0,msp | set master stack pointer
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#else
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jsr SYM (_Thread_Dispatch) | Perform context switch
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#endif
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#if ( M68K_COLDFIRE_ARCH == 0 )
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exit: moveml a7@+,d0-d1/a0-a1 | restore d0-d1,a0-a1
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#else
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exit: moveml a7@,d0-d1/a0-a1 | restore d0-d1,a0-a1
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lea a7@(SAVED),a7
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#endif
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#if ( M68K_HAS_VBR == 0 )
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addql #2,a7 | pop format/id
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#endif /* M68K_HAS_VBR */
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rte | return to thread
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| OR _Isr_dispatch
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/*PAGE
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* void _ISR_Dispatch()
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*
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* Entry point from the outermost interrupt service routine exit.
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* The current stack is the supervisor mode stack if this processor
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* has separate stacks.
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*
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* 1. save all registers not preserved across C calls.
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* 2. invoke the _Thread_Dispatch routine to switch tasks
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* or a signal to the currently executing task.
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* 3. restore all registers not preserved across C calls.
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* 4. return from interrupt
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*/
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.global SYM (_ISR_Dispatch)
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SYM (_ISR_Dispatch):
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#if ( M68K_COLDFIRE_ARCH == 0 )
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movml d0-d1/a0-a1,a7@-
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jsr SYM (_Thread_Dispatch)
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movml a7@+,d0-d1/a0-a1
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#else
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lea a7@(-SAVED),a7
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movml d0-d1/a0-a1,a7@
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jsr SYM (_Thread_Dispatch)
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movml a7@,d0-d1/a0-a1
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lea a7@(SAVED),a7
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#endif
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#if ( M68K_HAS_VBR == 0 )
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addql #2,a7 | pop format/id
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#endif /* M68K_HAS_VBR */
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rte
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