1 | .. comment SPDX-License-Identifier: CC-BY-SA-4.0 |
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2 | |
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3 | .. COMMENT: COPYRIGHT (c) 1988-2002. |
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4 | .. COMMENT: On-Line Applications Research Corporation (OAR). |
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5 | .. COMMENT: All rights reserved. |
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6 | |
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7 | Epiphany Specific Information |
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8 | ############################# |
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9 | |
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10 | This chapter discusses the`Epiphany Architecture |
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11 | http://adapteva.com/docs/epiphany_sdk_ref.pdf dependencies in this port of |
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12 | RTEMS. Epiphany is a chip that can come with 16 and 64 cores, each of which can |
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13 | run RTEMS separately or they can work together to run a SMP RTEMS application. |
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14 | |
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15 | **Architecture Documents** |
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16 | |
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17 | For information on the Epiphany architecture refer to the *Epiphany |
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18 | Architecture Reference* http://adapteva.com/docs/epiphany_arch_ref.pdf. |
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19 | |
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20 | Calling Conventions |
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21 | =================== |
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22 | |
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23 | Please refer to the *Epiphany SDK* |
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24 | http://adapteva.com/docs/epiphany_sdk_ref.pdf Appendix A: Application Binary |
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25 | Interface |
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26 | |
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27 | Floating Point Unit |
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28 | ------------------- |
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29 | |
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30 | A floating point unit is currently not supported. |
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31 | |
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32 | Memory Model |
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33 | ============ |
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34 | |
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35 | A flat 32-bit memory model is supported, no caches. Each core has its own 32 |
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36 | KiB strictly ordered local memory along with an access to a shared 32 MiB |
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37 | external DRAM. |
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38 | |
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39 | Interrupt Processing |
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40 | ==================== |
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41 | |
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42 | Every Epiphany core has 10 exception types: |
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43 | |
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44 | - Reset |
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45 | |
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46 | - Software Exception |
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47 | |
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48 | - Data Page Fault |
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49 | |
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50 | - Timer 0 |
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51 | |
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52 | - Timer 1 |
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53 | |
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54 | - Message Interrupt |
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55 | |
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56 | - DMA0 Interrupt |
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57 | |
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58 | - DMA1 Interrupt |
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59 | |
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60 | - WANT Interrupt |
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61 | |
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62 | - User Interrupt |
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63 | |
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64 | Interrupt Levels |
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65 | ---------------- |
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66 | |
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67 | There are only two levels: interrupts enabled and interrupts disabled. |
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68 | |
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69 | Interrupt Stack |
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70 | --------------- |
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71 | |
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72 | The Epiphany RTEMS port uses a dedicated software interrupt stack. The stack |
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73 | for interrupts is allocated during interrupt driver initialization. When an |
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74 | interrupt is entered, the _ISR_Handler routine is responsible for switching |
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75 | from the interrupted task stack to RTEMS software interrupt stack. |
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76 | |
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77 | Default Fatal Error Processing |
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78 | ============================== |
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79 | |
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80 | The default fatal error handler for this architecture performs the following |
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81 | actions: |
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82 | |
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83 | - disables operating system supported interrupts (IRQ), |
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84 | |
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85 | - places the error code in ``r0``, and |
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86 | |
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87 | - executes an infinite loop to simulate a halt processor instruction. |
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88 | |
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89 | Symmetric Multiprocessing |
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90 | ========================= |
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91 | |
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92 | SMP is not supported. |
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