2 * FreeRTOS Kernel V10.1.0
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3 * Copyright (C) 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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29 /*-----------------------------------------------------------
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30 * Implementation of functions defined in portable.h for the Tern EE 186
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32 *----------------------------------------------------------*/
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34 /* Library includes. */
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35 #include <embedded.h>
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38 /* Scheduler includes. */
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39 #include "FreeRTOS.h"
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41 #include "portasm.h"
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43 /* The timer increments every four clocks, hence the divide by 4. */
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44 #define portTIMER_COMPARE ( uint16_t ) ( ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) / ( uint32_t ) 4 )
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46 /* From the RDC data sheet. */
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47 #define portENABLE_TIMER_AND_INTERRUPT ( uint16_t ) 0xe001
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49 /* Interrupt control. */
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50 #define portEIO_REGISTER 0xff22
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51 #define portCLEAR_INTERRUPT 0x0008
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53 /* Setup the hardware to generate the required tick frequency. */
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54 static void prvSetupTimerInterrupt( void );
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56 /* The ISR used depends on whether the preemptive or cooperative scheduler
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58 #if( configUSE_PREEMPTION == 1 )
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59 /* Tick service routine used by the scheduler when preemptive scheduling is
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61 static void __interrupt __far prvPreemptiveTick( void );
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63 /* Tick service routine used by the scheduler when cooperative scheduling is
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65 static void __interrupt __far prvNonPreemptiveTick( void );
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68 /* Trap routine used by taskYIELD() to manually cause a context switch. */
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69 static void __interrupt __far prvYieldProcessor( void );
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71 /* The timer initialisation functions leave interrupts enabled,
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72 which is not what we want. This ISR is installed temporarily in case
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73 the timer fires before we get a change to disable interrupts again. */
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74 static void __interrupt __far prvDummyISR( void );
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76 /*-----------------------------------------------------------*/
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77 /* See header file for description. */
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78 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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80 StackType_t DS_Reg = 0;
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82 /* Place a few bytes of known values on the bottom of the stack.
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83 This is just useful for debugging. */
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85 *pxTopOfStack = 0x1111;
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87 *pxTopOfStack = 0x2222;
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89 *pxTopOfStack = 0x3333;
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92 /* We are going to start the scheduler using a return from interrupt
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93 instruction to load the program counter, so first there would be the
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94 function call with parameters preamble. */
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96 *pxTopOfStack = FP_SEG( pvParameters );
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98 *pxTopOfStack = FP_OFF( pvParameters );
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100 *pxTopOfStack = FP_SEG( pxCode );
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102 *pxTopOfStack = FP_OFF( pxCode );
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105 /* Next the status register and interrupt return address. */
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106 *pxTopOfStack = portINITIAL_SW;
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108 *pxTopOfStack = FP_SEG( pxCode );
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110 *pxTopOfStack = FP_OFF( pxCode );
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113 /* The remaining registers would be pushed on the stack by our context
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114 switch function. These are loaded with values simply to make debugging
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116 *pxTopOfStack = ( StackType_t ) 0xAAAA; /* AX */
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118 *pxTopOfStack = ( StackType_t ) 0xBBBB; /* BX */
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120 *pxTopOfStack = ( StackType_t ) 0xCCCC; /* CX */
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122 *pxTopOfStack = ( StackType_t ) 0xDDDD; /* DX */
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124 *pxTopOfStack = ( StackType_t ) 0xEEEE; /* ES */
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127 /* We need the true data segment. */
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128 __asm{ MOV DS_Reg, DS };
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130 *pxTopOfStack = DS_Reg; /* DS */
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132 *pxTopOfStack = ( StackType_t ) 0x0123; /* SI */
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134 *pxTopOfStack = ( StackType_t ) 0xDDDD; /* DI */
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136 *pxTopOfStack = ( StackType_t ) 0xBBBB; /* BP */
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138 return pxTopOfStack;
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140 /*-----------------------------------------------------------*/
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142 BaseType_t xPortStartScheduler( void )
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144 /* This is called with interrupts already disabled. */
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146 /* Put our manual switch (yield) function on a known
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148 setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );
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150 /* Setup the tick interrupt. */
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151 prvSetupTimerInterrupt();
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153 /* Kick off the scheduler by setting up the context of the first task. */
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154 portFIRST_CONTEXT();
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156 /* Should not get here! */
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159 /*-----------------------------------------------------------*/
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161 static void __interrupt __far prvDummyISR( void )
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163 /* The timer initialisation functions leave interrupts enabled,
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164 which is not what we want. This ISR is installed temporarily in case
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165 the timer fires before we get a change to disable interrupts again. */
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166 outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
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168 /*-----------------------------------------------------------*/
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170 /* The ISR used depends on whether the preemptive or cooperative scheduler
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172 #if( configUSE_PREEMPTION == 1 )
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173 static void __interrupt __far prvPreemptiveTick( void )
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175 /* Get the scheduler to update the task states following the tick. */
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176 if( xTaskIncrementTick() != pdFALSE )
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178 /* Switch in the context of the next task to be run. */
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179 portSWITCH_CONTEXT();
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182 /* Reset interrupt. */
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183 outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
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186 static void __interrupt __far prvNonPreemptiveTick( void )
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188 /* Same as preemptive tick, but the cooperative scheduler is being used
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189 so we don't have to switch in the context of the next task. */
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190 xTaskIncrementTick();
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192 /* Reset interrupt. */
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193 outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
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196 /*-----------------------------------------------------------*/
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198 static void __interrupt __far prvYieldProcessor( void )
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200 /* Switch in the context of the next task to be run. */
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201 portSWITCH_CONTEXT();
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203 /*-----------------------------------------------------------*/
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205 void vPortEndScheduler( void )
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207 /* Not implemented. */
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209 /*-----------------------------------------------------------*/
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211 static void prvSetupTimerInterrupt( void )
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213 const uint16_t usTimerACompare = portTIMER_COMPARE, usTimerAMode = portENABLE_TIMER_AND_INTERRUPT;
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214 const uint16_t usT2_IRQ = 0x13;
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216 /* Configure the timer, the dummy handler is used here as the init
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217 function leaves interrupts enabled. */
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218 t2_init( usTimerAMode, usTimerACompare, prvDummyISR );
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220 /* Disable interrupts again before installing the real handlers. */
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221 portDISABLE_INTERRUPTS();
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223 #if( configUSE_PREEMPTION == 1 )
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224 /* Tick service routine used by the scheduler when preemptive scheduling is
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226 setvect( usT2_IRQ, prvPreemptiveTick );
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228 /* Tick service routine used by the scheduler when cooperative scheduling is
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230 setvect( usT2_IRQ, prvNonPreemptiveTick );
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