1 ; FreeRTOS.org V4.0.5 - Copyright (C) 2003-2006 Richard Barry.
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3 ; This file is part of the FreeRTOS.org distribution.
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5 ; FreeRTOS.org is free software; you can redistribute it and/or modify
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6 ; it under the terms of the GNU General Public License as published by
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7 ; the Free Software Foundation; either version 2 of the License, or
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8 ; (at your option) any later version.
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10 ; FreeRTOS.org is distributed in the hope that it will be useful,
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11 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 ; GNU General Public License for more details.
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15 ; You should have received a copy of the GNU General Public License
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16 ; along with FreeRTOS.org; if not, write to the Free Software
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17 ; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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19 ; A special exception to the GPL can be applied should you wish to distribute
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20 ; a combined work that includes FreeRTOS.org, without being obliged to provide
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21 ; the source code for any proprietary components. See the licensing section
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22 ; of http://www.FreeRTOS.org for full details of how and when the exception
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25 ; ***************************************************************************
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26 ; See http://www.FreeRTOS.org for documentation, latest information, license
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27 ; and contact details. Please ensure to read the configuration and relevant
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28 ; port sections of the online documentation.
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29 ; ***************************************************************************
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33 ; Declare all extern symbols here - including any ISRs that are referenced in
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38 EXTERN SIG_OUTPUT_COMPARE1A
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39 EXTERN SIG_UART_RECV
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40 EXTERN SIG_UART_DATA
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43 ; Functions used by scheduler
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44 ; ---------------------------
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45 EXTERN vTaskSwitchContext
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47 EXTERN vTaskIncrementTick
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48 EXTERN uxCriticalNesting
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50 ; Functions implemented in this file
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51 ; ----------------------------------
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53 PUBLIC vPortYieldFromTick
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57 ; Interrupt vector table.
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58 ; -----------------------
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60 ; For simplicity the RTOS tick interrupt routine uses the __task keyword.
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61 ; As the IAR compiler does not permit a function to be declared using both
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62 ; __task and __interrupt, the use of __task necessitates that the interrupt
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63 ; vector table be setup manually.
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65 ; To write an ISR, implement the ISR function using the __interrupt keyword
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66 ; but do not install the interrupt using the "#pragma vector=ABC" method.
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67 ; Instead manually place the name of the ISR in the vector table using an
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68 ; ORG and jmp instruction as demonstrated below.
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69 ; You will also have to add an EXTERN statement at the top of the file.
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74 ORG TIMER1_COMPA_vect ; Vector address
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75 jmp SIG_OUTPUT_COMPARE1A ; ISR
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77 ORG USART_RXC_vect ; Vector address
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78 jmp SIG_UART_RECV ; ISR
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80 ORG USART_UDRE_vect ; Vector address
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81 jmp SIG_UART_DATA ; ISR
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88 ; Saving and Restoring a Task Context and Task Switching
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89 ; ------------------------------------------------------
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91 ; The IAR compiler does not fully support inline assembler, so saving and
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92 ; restoring a task context has to be written in an asm file.
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94 ; vPortYield() and vPortYieldFromTick() are usually written in C. Doing
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95 ; so in this case would required calls to be made to portSAVE_CONTEXT() and
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96 ; portRESTORE_CONTEXT(). This is dis-advantageous as the context switch
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97 ; function would require two extra jump and return instructions over the
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98 ; WinAVR equivalent.
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100 ; To avoid this I have opted to implement both vPortYield() and
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101 ; vPortYieldFromTick() in this assembly file. For convenience
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102 ; portSAVE_CONTEXT and portRESTORE_CONTEXT are implemented as macros.
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104 portSAVE_CONTEXT MACRO
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105 st -y, r0 ; First save the r0 register - we need to use this.
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106 in r0, SREG ; Obtain the SREG value so we can disable interrupts...
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107 cli ; ... as soon as possible.
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108 st -y, r0 ; Store the SREG as it was before we disabled interrupts.
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110 in r0, SPL ; Next store the hardware stack pointer. The IAR...
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111 st -y, r0 ; ... compiler uses the hardware stack as a call stack ...
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112 in r0, SPH ; ... only.
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115 st -y, r1 ; Now store the rest of the registers. Dont store the ...
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116 st -y, r2 ; ... the Y register here as it is used as the software
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117 st -y, r3 ; stack pointer and will get saved into the TCB.
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144 lds r0, uxCriticalNesting
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145 st -y, r0 ; Store the critical nesting counter.
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147 lds r26, pxCurrentTCB ; Finally save the software stack pointer (Y ...
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148 lds r27, pxCurrentTCB + 1 ; ... register) into the TCB.
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155 portRESTORE_CONTEXT MACRO
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156 lds r26, pxCurrentTCB
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157 lds r27, pxCurrentTCB + 1 ; Restore the software stack pointer from ...
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158 ld r28, x+ ; the TCB into the software stack pointer (...
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159 ld r29, x+ ; ... the Y register).
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162 sts uxCriticalNesting, r0
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163 ld r31, y+ ; Restore the registers down to R0. The Y
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164 ld r30, y+ ; register is missing from this list as it
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165 ld r27, y+ ; has already been restored.
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193 ld r0, y+ ; The next thing on the stack is the ...
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194 out SPH, r0 ; ... hardware stack pointer.
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198 ld r0, y+ ; Next there is the SREG register.
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201 ld r0, y+ ; Finally we have finished with r0, so restore r0.
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207 ; vPortYield() and vPortYieldFromTick()
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208 ; -------------------------------------
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210 ; Manual and preemptive context switch functions respectively.
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211 ; The IAR compiler does not fully support inline assembler,
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212 ; so these are implemented here rather than the more usually
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213 ; place of within port.c.
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216 portSAVE_CONTEXT ; Save the context of the current task.
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217 call vTaskSwitchContext ; Call the scheduler.
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218 portRESTORE_CONTEXT ; Restore the context of whichever task the ...
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219 ret ; ... scheduler decided should run.
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221 vPortYieldFromTick:
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222 portSAVE_CONTEXT ; Save the context of the current task.
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223 call vTaskIncrementTick ; Call the timer tick function.
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224 call vTaskSwitchContext ; Call the scheduler.
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225 portRESTORE_CONTEXT ; Restore the context of whichever task the ...
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226 ret ; ... scheduler decided should run.
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231 ; Again due to the lack of inline assembler, this is required
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232 ; to get access to the portRESTORE_CONTEXT macro.
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235 portRESTORE_CONTEXT
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239 ; Just a filler for unused interrupt vectors.
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