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1
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- data that is needed from both app and dfu mode
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2
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- code that is needed from both app and dfu mode
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3
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- function pointers
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4
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- copy code to RAM in case of DFU switch
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5
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- data that is only needed in DFU mode
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6
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- can be overwritten in case of reset-to-application
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7
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- data that is only needed in app mode
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8
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- can be overwritten with DFU data in case of DFU switch
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9
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- code that is only needed in DFU mode
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10
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- has to be copied to ram in case of DFU switch
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11
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- code that is only needed in app mode
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12
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- can be read from flash, no action required
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13
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14
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15
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=> abandoned that complicated idea.
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16
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now all DFU functions are __ramfunc's and thus always present.
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17
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18
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19
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interaction between app and dfu code:
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20
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21
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- dfu_switch(void)
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22
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- dfu_status (can be put in accessor function, if required)
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23
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- dfu_cfg_descriptor
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24
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- dfu_dev_descriptor
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25
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- dfu_ep0_handler()
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26
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27
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28
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order of events at boot;
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29
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30
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- start at reset vector in flash
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31
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- AT91F_LowLevelInit()
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32
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- setup stack for each mode
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33
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- relocate 'data' of bootloader, including ramfunc/vectram
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34
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- clear 'bss' of bootloader
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35
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- call remap command
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36
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- call usb initialization (irq, clock)
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37
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- if keypress,
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38
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- call dfu_main()
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39
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- wait for ep0 / busreset interrupt
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40
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- else call main()
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41
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42
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43
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memory layout:
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44
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45
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0: lowlevel startup code
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46
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Cstartup.o 0x00bc
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47
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Cstartup_SAM7.o 0x0100
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48
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dfufunc 0x1dcc
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49
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dfustruct 0x0038
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50
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51
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text text 0x0070
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52
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data data 0x0000
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53
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bss bss 0x000c
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54
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55
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flash = text + data (= 8k)
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56
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ram/rel = data + bss (12 bytes)
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57
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|
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58
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|
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59
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If we drop the DFU-can-flash-DFU requirement, we can leave all DFU related code
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60
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in flash. no need for any function to be permanently in RAM. However, not
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61
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preventing this feature in some future version, we shouldn't do that.
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62
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63
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64
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Function DFU runtime
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65
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udp_init x x RAM
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66
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udp_ep0_send_data x x RAM
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67
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udp_ep0_send_zlp x x RAM
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68
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udp_sp0_send_stall x x RAM
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69
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handle_dnload x - flash/relocated
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70
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handle_upload x - flash/relocated
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71
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handle_getstatus x - flash/relocated
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72
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handle_getstate x - flash/relocated
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73
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dfu_ep0_handler x x RAM
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74
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75
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dfu_dev_descriptor x - flash/relocated
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76
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dfu_cfg_descriptor x - flash/relocated
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77
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dfu_udp_ep0_handler x - flash/relocated
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78
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dfu_udp_irq x - flash/relocated
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79
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dfu_switch - x RAM
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80
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dfu_main x - flash/relocated
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81
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vectram x x flash/relocated/switched
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82
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IRQ_Handler_EntryR x x flash/relocated/switched
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83
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_remap x - flash/reloaded
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84
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85
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dfu_api x x flash (const anyway)
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86
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dfu_state x x RAM
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87
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|
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88
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|
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89
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preconditions:
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90
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- dfu code assumes to be loaded to address zero to make it work from both ram and rom
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91
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|
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92
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startup:
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93
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- exception vectors (in flash)
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94
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- call lowlevel_init
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95
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- setup user/supervisor/FIQ/IRQ stack
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96
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- relocate dfu_state
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97
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- if DFU switch is pressed
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98
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- jump to dfu_main in flash
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99
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- relocate all of DFU .text/.data into ram (including exception vectors)
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100
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- initialize DFU .bss
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101
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- remap RAM to address zero
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102
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|
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103
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- if DFU switch is not pressed jump to entry address of app
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104
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- Cstartup_app.S
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105
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- relocate application .data
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106
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- initialize application .bss
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107
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- jump to appliction main
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108
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- application uses dfu_api in flash, pointing to in-flash data
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109
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- application calls dfu_switch()
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110
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- disable all interupts but USB
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111
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- relocate all of DFU .text/.data into ram (including exception vectors)
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112
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- remap RAM to address zero
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113
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- check whether app has already remapped RAM before !?!
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|
114
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|
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115
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memory map:
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116
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117
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load_addr run_Addr
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118
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0x00100000 0x00000000 exception vectors (DFU Cstartup)
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119
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Cstartup_SAM7
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120
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121
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0x00200000
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122
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|
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123
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|
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124
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DFU constants:
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125
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_etext:
|
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126
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_data: 0x200000
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|
127
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_edata:
|
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128
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|
|
129
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APP contants:
|
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130
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_data: _edata_dfu
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131
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