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99 lines
2.1 KiB
C
99 lines
2.1 KiB
C
/*
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task - cooperative multitasking
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Copyright (C) 2011 Pavel Semerad
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "task.h"
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// main OPER task
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TCB OPER;
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// pointer to current task
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TCB *ptid;
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// initialise tasks
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void task_init(void) {
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// initialize current task id
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ptid = &OPER;
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// OPER is running -> running task has ASLEEP state
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sleep(OPER);
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// initialize LINK in OPER task
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OPER.link = &OPER;
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}
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// activate task - set pointers and AWAKE
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void _do_activate(TCB *task, u8 *stack, u16 stack_size,
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void (*function)(void)) {
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u8 *stack_ret = stack + stack_size - 2;
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*(u16 *)stack_ret = (u16)function;
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task->hwstack = stack_ret - 1; // SP points below last value
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task->status = _AWAKE;
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}
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// build - link in task
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void _do_build(TCB *task) {
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task->status = _ASLEEP; // do not run this yet
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task->link = OPER.link;
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OPER.link = task;
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}
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// pause current task and try to run another one
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void pause(void) {
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#asm
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; set _AWAKE
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ldw X, _ptid
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ld A, #255
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ld (X), A
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_pause_stop:
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; save HW stack pointer
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ldw Y, SP
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ldw (3, X), Y
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; find next _AWAKE task - if none, loop
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__xpause:
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ldw X, (1, X)
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ld A, (X)
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jreq __xpause ; skip _ASLEEP task
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; _AWAKE task found, restore HW stack pointer
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ldw Y, X
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ldw X, (3, X)
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sim
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ldw SP, X
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rim
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; set _ASLEEP - current task has this state
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clr A
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ld (Y), A
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; set ptid to this task
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ldw _ptid, Y
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#endasm
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}
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// stop current task and try to run another one
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void stop(void) {
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#asm
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ldw X, _ptid
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jra _pause_stop
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#endasm
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}
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