1 | ################################################################################# |
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2 | # File : reset.s |
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3 | # Author : Alain Greiner |
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4 | # Date : 15/09/2010 |
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5 | ################################################################################# |
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6 | # This is an improved boot code : |
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7 | # - It initializes the Status Register (SR) |
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8 | # - It defines the stack size and initializes the stack pointer ($29) |
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9 | # - It initializes the interrupt vector with two ISR addresses. |
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10 | # - It configurates the ICU : IRQ_IN[0] & IRQ_IN[1] activated. |
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11 | # - It initializes the EPC register, and jumps to the main in user mode. |
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12 | ################################################################################# |
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13 | |
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14 | .section .reset,"ax",@progbits |
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15 | |
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16 | .extern seg_stack_base |
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17 | .extern seg_data_base |
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18 | .extern main |
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19 | .extern _interrupt_vector |
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20 | .extern _isr_tty_get_task0 |
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21 | .extern _isr_timer |
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22 | |
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23 | .globl reset # makes reset an external symbol |
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24 | .ent reset |
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25 | .align 2 |
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26 | |
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27 | reset: |
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28 | .set noreorder |
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29 | |
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30 | # initializes stack pointer |
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31 | la $29, seg_stack_base |
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32 | addiu $29, $29, 0x4000 |
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33 | |
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34 | # initializes interrupt vector |
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35 | la /* A COMPLETER */ # $26 <= interrupt_vector address |
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36 | la /* A COMPLETER */ # $27 <= isr_timer address |
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37 | sw /* A COMPLETER */ # interrupt_vector[0] <= _isr_timer |
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38 | la /* A COMPLETER */ # $27 <= isr_tty_get_task0 address |
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39 | sw /* A COMPLETER */ # interrupt_vector[1] <= _isr_tty_get_task0 |
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40 | |
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41 | # initializes ICU |
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42 | la $26, seg_icu_base |
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43 | li $27, 0x3 # IRQ_IN[0] & IRQ_IN[1] enabled |
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44 | sw $27, 8($26) # ICU_MASK_SET 0x3 |
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45 | |
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46 | # initializes SR register |
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47 | li $26, 0x0000FF13 # IRQ activation |
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48 | mtc0 $26, $12 |
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49 | |
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50 | # jump to main in user mode |
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51 | la $26, main |
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52 | mtc0 $26, $14 |
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53 | eret |
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54 | |
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55 | .end reset |
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56 | .size reset, .-reset |
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57 | |
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58 | .set reorder |
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