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253 2 {
254 3 Message_byte_G = 1;
255 3 }
256 2 else
257 2 {
258 3 Message_byte_G = 0;
259 3 }
260 2
261 2 // Check tick data - send ack if necessary
262 2 // NOTE: 'START' message will only be sent after a 'time out'
263 2 if (SCU_B_SLAVE_Process_Tick_Message() == SLAVE_ID)
264 2 {
265 3 SCU_B_SLAVE_Send_Ack_Message_To_Master();
266 3
267 3 // Feed the watchdog ONLY when a *relevant* message is received
268 3 // (noise on the bus, etc, will not stop the watchdog...)
269 3 //
270 3 // START messages will NOT refresh the slave
271 3 // - Must talk to every slave at regular intervals
272 3 SCU_B_SLAVE_Watchdog_Refresh();
273 3 }
274 2
275 2 // NOTE: calculations are in *TICKS* (not milliseconds)
276 2 for (Index = 0; Index < SCH_MAX_TASKS; Index++)
277 2 {
278 3 // Check if there is a task at this location
279 3 if (SCH_tasks_G[Index].pTask)
280 3 {
281 4 if (SCH_tasks_G[Index].Delay == 0)
282 4 {
283 5 // The task is due to run
284 5 SCH_tasks_G[Index].RunMe = 1; // Set the run flag
285 5
286 5 if (SCH_tasks_G[Index].Period)
287 5 {
288 6 // Schedule periodic tasks to run again
289 6 SCH_tasks_G[Index].Delay = SCH_tasks_G[Index].Period;
290 6 }
291 5 }
292 4 else
293 4 {
294 5 // Not yet ready to run: just decrement the delay
295 5 SCH_tasks_G[Index].Delay -= 1;
296 5 }
297 4 }
298 3 }
299 2 RI = 0; // Reset the RI flag
300 2 }
301 1 else
302 1 {
303 2 // ISR call was triggered by TI flag, after last character was sent
C51 COMPILER V6.10 SCU_BS 04/19/2001 13:59:49 PAGE 6
304 2
305 2 // RS485_Tx_Enable flag is reset here
306 2 RS485_Tx_Enable = 0;
307 2
308 2 // Must clear the TI flag
309 2 TI = 0;
310 2 }
311 1 }
312
313 /*------------------------------------------------------------------*-
314
315 SCU_B_SLAVE_Send_Ack_Message_To_Master()
316
317 Slave must send and 'Acknowledge' message to the master, after
318 tick messages are received. NOTE: Only tick messages specifically
319 addressed to this slave should be acknowledged.
320
321 The acknowledge message serves two purposes:
322 [1] It confirms to the master that this slave is alive & well.
323 [2] It provides a means of sending data to the master and - hence
324 - to other slaves.
325
326 NOTE: Direct data transfer between slaves is NOT possible.
327
328 -*------------------------------------------------------------------*/
329 void SCU_B_SLAVE_Send_Ack_Message_To_Master(void)
330 {
331 1 // Enable the slave RS-485 hardware (Tx)
332 1 // NOTE: This flag will be reset in the 'Update' ISR
333 1 RS485_Tx_Enable = 1;
334 1
335 1 // Sending one byte of data at a time, depending on index value
336 1 // If Message_byte_G is 0, send first byte (the slave ID)
337 1 if (Message_byte_G == 0)
338 1 {
339 2 TI = 0;
340 2 TB8 = 1; // Set 'Command' bit
341 2 SBUF = SLAVE_ID;
342 2 }
343 1 else
344 1 {
345 2 // Message_byte_G is 1, send the data byte
346 2 TI = 0;
347 2 TB8 = 0;
348 2 SBUF = Ack_message_data_G;
349 2 }
350 1
351 1 // Data sent - return
352 1 }
353
354 /*------------------------------------------------------------------*-
355
356 SCU_B_SLAVE_Process_Tick_Message()
357
358 The ticks messages are crucial to the operation of this shared-clock
359 scheduler: the arrival of a tick message (at regular intervals)
360 invokes the 'Update' ISR, that drives the scheduler.
361
362 The tick messages themselves may contain data. These data are
363 extracted in this function.
364
365 -*------------------------------------------------------------------*/
C51 COMPILER V6.10 SCU_BS 04/19/2001 13:59:49 PAGE 7
366 tByte SCU_B_SLAVE_Process_Tick_Message(void)
367 {
368 1 tByte Data;
369 1
370 1 // Try to get data byte
371 1 if (RI == 0)
372 1 {
373 2 // No data - something is wrong
374 2
375 2 // Set the error flag bit
376 2 Network_error_pin = NETWORK_ERROR;
377 2
378 2 // Return slave ID 0
379 2 return 0x00;
380 2 }
381 1
382 1 // There *ARE* data available
383 1 Data = (tByte) SBUF;
384 1 RI = 0; // Clear RI flag
385 1
386 1 // What we do with this message depends if it a first or second byte
387 1 if (Message_byte_G == 0)
388 1 {
389 2 // This is (should be) an ID byte
390 2 Message_ID_G = Data;
391 2
392 2 if (RB8 == 0)
393 2 {
394 3 Message_ID_G = 0; // Command bit should be set
395 3 }
396 2 }
397 1 else
398 1 {
399 2 // This is (should be) a data byte
400 2 // - Command bit should not be set
401 2 if ((Message_ID_G == SLAVE_ID) && (RB8 == 0))
402 2 {
403 3 Tick_message_data_G = Data;
404 3 }
405 2 else
406 2 {
407 3 // Something is wrong - set Message_ID to 0
408 3 Message_ID_G = 0;
409 3
410 3 // Set the error flag bit
411 3 Network_error_pin = NETWORK_ERROR;
412 3 }
413 2 }
414 1
415 1 return Message_ID_G;
416 1 }
417
418
419 /*------------------------------------------------------------------*-
420
421 SCU_B_SLAVE_Watchdog_Init()
422
423 This function sets up the watchdog timer.
424
425 If the Master fails (or other error develop),
426 no tick messages will arrive, and the scheduler
427 will stop.
C51 COMPILER V6.10 SCU_BS 04/19/2001 13:59:49 PAGE 8
428
429 To detect this situation, we have a (hardware) watchdog
430 running in the slave. This watchdog - which should be set to
431 overflow at around 100ms - is used to set the system into a
432 known (safe) state. The slave will then wait (indefinitely)
433 for the problem to be resolved.
434
435 NOTE: The slave will not be generating Ack messages in these
436 circumstances. The Master (if running) will therefore be aware
437 that there is a problem.
438
439 -*------------------------------------------------------------------*/
440 void SCU_B_SLAVE_Watchdog_Init(void)
441 {
442 1 // INIT NOT REQUIRED FOR 1232 EXTERNAL WATCHDOG
443 1 // - May be required wwith different watchdog hardware
444 1 //
445 1 // Edit as required
446 1 }
447
448
449 /*------------------------------------------------------------------*-
450
451 SCU_B_SLAVE_Watchdog_Refresh()
452
453 Feed the external (1232) watchdog.
454
455 Timeout is between ~60 and 250 ms (hardware dependent)
456
457 Assumes external 1232 watchdog
458
459 -*------------------------------------------------------------------*/
460 void SCU_B_SLAVE_Watchdog_Refresh(void) reentrant
461 {
462 1 // Change the state of the watchdog pin
463 1 if (WATCHDOG_state_G == 1)
464 1 {
465 2 WATCHDOG_state_G = 0;
466 2 WATCHDOG_pin = 0;
467 2 }
468 1 else
469 1 {
470 2 WATCHDOG_state_G = 1;
471 2 WATCHDOG_pin = 1;
472 2 }
473 1 }
474
475 /*------------------------------------------------------------------*-
476
477 SCU_B_SLAVE_Enter_Safe_State()
478
479 This is the state enterted by the system when:
480 (1) The node is powered up or reset
481 (2) The Master node fails, and no working backup is available
482 (3) The network has an error
483 (4) Tick messages are delayed for any other reason
484
485 Try to ensure that the system is in a 'safe' state in these
486 circumstances.
487
488 -*------------------------------------------------------------------*/
489 void SCU_B_SLAVE_Enter_Safe_State(void)
C51 COMPILER V6.10 SCU_BS 04/19/2001 13:59:49 PAGE 9
490 {
491 1 // USER DEFINED - Edit as required
492 1 TRAFFIC_LIGHTS_Display_Safe_Output();
493 1 }
494
495 /*------------------------------------------------------------------*-
496 ---- END OF FILE -------------------------------------------------
497 -*------------------------------------------------------------------*/
498
MODULE INFORMATION: STATIC OVERLAYABLE
CODE SIZE = 427 ----
CONSTANT SIZE = ---- ----
XDATA SIZE = ---- ----
PDATA SIZE = ---- ----
DATA SIZE = 3 5
IDATA SIZE = ---- ----
BIT SIZE = 2 1
END OF MODULE INFORMATION.
C51 COMPILATION COMPLETE. 0 WARNING(S), 0 ERROR(S)
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