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File List  |  1992-04-28  |  4KB  |  133 lines
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  4. Motorola DSP56000 Assembler  Version 3.1.12  91-12-16  13:55:22  boot.asm  Page 1
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  8. 1                        ;*****************************************************************************
  9. 2                        ;  This routine demonstrates how to construct a module which will boot
  10. 3                        ;  from an external byte-wide EPROM and execute in on-chip Program RAM.
  11. 4                        ;
  12. 5                        ;  The main routine simply toggles the least significant bit of Port-C
  13. 6                        ;  and this activity can be monitored externally with an oscilloscope
  14. 7                        ;  to confirm that the boot occurred correctly.
  15. 8                        ;
  16. 9                        ;  assemble this routine with the following command line:
  17. 10                       ;     asm56000 -a -b -l boot
  18. 11                       ;
  19. 12                       ;  build the S-Record file for use by the PROM-Burner via the SREC utility:
  20. 13                       ;     SREC boot
  21. 14                       ;
  22. 15                       ;  The vectors will be placed into the EPROM at address $C000 and the 
  23. 16                       ;  main routine will start at $C0F0 in the EPROM. 
  24. 17                       ;*****************************************************************************
  25. 18        00FFE1         m_pcc     equ     $FFE1                             ;Port-C control register address (in X:)
  26. 19        00FFE3         m_pcddr   equ     $FFE3                             ;Port-C data direction register
  27. 20        00FFE5         m_pcd     equ     $FFE5                             ;Port-C data register
  28. 21        000050         main      equ     $50                               ;main routine starting address
  29. 22        000000         RUNTIME   equ     0                                 ;bootstrap into P:0
  30. 23        00C000         LOADTIME  equ     $C000                             ;load into EPROM at P:$C000
  31. 24     
  32. 25                                 page    132,66,3,3                        ;format the page for 132 columns, 66 lines
  33. 26     
  34. 27     
  35. 28        P:0000 P:C000                   org     P:RUNTIME,P:LOADTIME
  36. 29        P:0000 P:C000 0D0050            jsr     <GO_1                             ;RESET Vector...start program
  37. 30        P:0001 P:C001 000000            nop                                       ;...vectors have 2 words...
  38. 31     
  39. 32                                        DUP     62                                ;define unused vectors with
  40. 33   m                                    nop                                       ;..."safe" default routine
  41. 34   m                                    nop
  42. 35   m                                    ENDM
  43. 160    
  44. 161    
  45. 162       P:0050 P:C0F0                   org     P:main,P:LOADTIME+(3*main)
  46. 163                             GO_1
  47. 164                                                                                 ;**** simple routine to toggle I/O pin ****
  48. 165       P:0050 P:C0F0 08F4A3            movep             #$0001,x:m_pcddr        ;only lsb of Port-C will be an output
  49.                         000001
  50. 166       P:0052 P:C0F2 08F4A1            movep             #$0000,x:m_pcc          ;all Port-C pins will be G.P. I/O
  51.                         000000
  52. 167                             _loop
  53. 168       P:0054 P:C0F4 0BA500            bchg    #0,x:m_pcd                        ;toggle the lsb of Port-C
  54. 169       P:0055 P:C0F5 0C0054            jmp     <_loop
  55. 170    
  56. 171       000056                CodeSize  set     *
  57. 172    
  58. 173                             ;
  59. 174                             ;    test to see if the code size exceeds the available on-chip resources
  60. 175                             ;           (512 words in on-chip P:RAM)
  61. 176                             ;
  62. 177                                       IF      CodeSize>$1FF
  63. 181                                       ENDIF
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  70. Motorola DSP56000 Assembler  Version 3.1.12  91-12-16  13:55:22  boot.asm  Page 2
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  74. 182    
  75. 183                                       END
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