begriffs open source - cmsis-freertos/blob - Source/portable/oWatcom/16BitDOS/Flsh186/port.c

136 /* Points to the original routine installed on the vector we use for manual context switches. This is then used to restore the original routine during prvExitFunction(). */

137 static void ( __interrupt __far *pxOldSwitchISR )();

138

139 /* Used to restore the original DOS context when the scheduler is ended. */

140 static jmp_buf xJumpBuf;

141

142 /*lint +e956 */

143

144 /*-----------------------------------------------------------*/

145 BaseType_t xPortStartScheduler( void )

146 {

147 /* This is called with interrupts already disabled. */

148

149 /* Remember what was on the interrupts we are going to use

150 so we can put them back later if required. */

151 pxOldSwitchISR = _dos_getvect( portSWITCH_INT_NUMBER );

152

153 /* Put our manual switch (yield) function on a known

154 vector. */

155 _dos_setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );

156

157 #if configUSE_PREEMPTION == 1

158 {

159 /* Put our tick switch function on the timer interrupt. */

160 _dos_setvect( portTIMER_INT_NUMBER, prvPreemptiveTick );

161 }

162 #else

163 {

164 /* We want the timer interrupt to just increment the tick count. */

165 _dos_setvect( portTIMER_INT_NUMBER, prvNonPreemptiveTick );

166 }

167 #endif

168

169 prvSetTickFrequency( configTICK_RATE_HZ );

170

171 /* Clean up function if we want to return to DOS. */

172 if( setjmp( xJumpBuf ) != 0 )

173 {

174 prvExitFunction();

175 sSchedulerRunning = pdFALSE;

176 }

177 else

178 {

179 sSchedulerRunning = pdTRUE;

180

181 /* Kick off the scheduler by setting up the context of the first task. */

182 portFIRST_CONTEXT();

183 }

184

185 return sSchedulerRunning;

186 }

187 /*-----------------------------------------------------------*/

188

189 /* The tick ISR used depend on whether or not the preemptive or cooperative

190 kernel is being used. */

191 #if configUSE_PREEMPTION == 1

192 static void __interrupt __far prvPreemptiveTick( void )

193 {

194 /* Get the scheduler to update the task states following the tick. */

195 if( xTaskIncrementTick() != pdFALSE )

196 {

197 /* Switch in the context of the next task to be run. */

198 portSWITCH_CONTEXT();

199 }

200

201 /* Reset the PIC ready for the next time. */

202 portRESET_PIC();

203 }

204 #else

205 static void __interrupt __far prvNonPreemptiveTick( void )

206 {

207 /* Same as preemptive tick, but the cooperative scheduler is being used

208 so we don't have to switch in the context of the next task. */

209 xTaskIncrementTick();

210 portRESET_PIC();

211 }

212 #endif

213 /*-----------------------------------------------------------*/

214

215 static void __interrupt __far prvYieldProcessor( void )

216 {

217 /* Switch in the context of the next task to be run. */

218 portSWITCH_CONTEXT();

219 }

220 /*-----------------------------------------------------------*/

221

222 void vPortEndScheduler( void )

223 {

224 /* Jump back to the processor state prior to starting the

225 scheduler. This means we are not going to be using a

226 task stack frame so the task can be deleted. */

227 longjmp( xJumpBuf, 1 );

228 }

229 /*-----------------------------------------------------------*/

230

231 static void prvExitFunction( void )

232 {

233 const uint16_t usTimerDisable = 0x0000;

234 uint16_t usTimer0Control;

235

236 /* Interrupts should be disabled here anyway - but no

237 harm in making sure. */

238 portDISABLE_INTERRUPTS();

239 if( sSchedulerRunning == pdTRUE )

240 {

241 /* Put back the switch interrupt routines that was in place

242 before the scheduler started. */

243 _dos_setvect( portSWITCH_INT_NUMBER, pxOldSwitchISR );

244 }

245

246 /* Disable the timer used for the tick to ensure the scheduler is

247 not called before restoring interrupts. There was previously nothing

248 on this timer so there is no old ISR to restore. */

249 portOUTPUT_WORD( portTIMER_1_CONTROL_REGISTER, usTimerDisable );

250

251 /* Restart the DOS tick. */

252 usTimer0Control = portINPUT_WORD( portTIMER_0_CONTROL_REGISTER );

253 usTimer0Control |= portTIMER_INTERRUPT_ENABLE;

254 portOUTPUT_WORD( portTIMER_0_CONTROL_REGISTER, usTimer0Control );

255

256

257 portENABLE_INTERRUPTS();

258 }

259 /*-----------------------------------------------------------*/

260

261 static void prvSetTickFrequency( uint32_t ulTickRateHz )

262 {

263 const uint16_t usMaxCountRegister = 0xff5a;

264 const uint16_t usTimerPriorityRegister = 0xff32;

265 const uint16_t usTimerEnable = 0xC000;

266 const uint16_t usRetrigger = 0x0001;

267 const uint16_t usTimerHighPriority = 0x0000;

268 uint16_t usTimer0Control;

269

270 /* ( CPU frequency / 4 ) / clock 2 max count [inpw( 0xff62 ) = 7] */

271

272 const uint32_t ulClockFrequency = 0x7f31a0;

273

274 uint32_t ulTimerCount = ulClockFrequency / ulTickRateHz;

275

276 portOUTPUT_WORD( portTIMER_1_CONTROL_REGISTER, usTimerEnable | portTIMER_INTERRUPT_ENABLE | usRetrigger );

277 portOUTPUT_WORD( usMaxCountRegister, ( uint16_t ) ulTimerCount );

278 portOUTPUT_WORD( usTimerPriorityRegister, usTimerHighPriority );

279

280 /* Stop the DOS tick - don't do this if you want to maintain a TOD clock. */

281 usTimer0Control = portINPUT_WORD( portTIMER_0_CONTROL_REGISTER );

282 usTimer0Control &= ~portTIMER_INTERRUPT_ENABLE;

283 portOUTPUT_WORD( portTIMER_0_CONTROL_REGISTER, usTimer0Control );

284 }

285

286

287 /*lint +e950 */

288