SP points at last pushed byte

diff --git a/ao_task.c b/ao_task.c
index 4f7387e310f595fe921b6a3b3c604d2ebd934ce3..a0c39ec9b70bbd970c2dacf91d27cf9edd995a39 100644 (file)
--- a/ao_task.c
+++ b/ao_task.c
@@ -74,9 +74,9 @@ ao_yield(void) _naked
                /* Push ACC first, as when restoring the context it must be restored
                 * last (it is used to set the IE register). */
                push    ACC
-               /* Store the IE register then disable interrupts. */
+               /* Store the IE register then enable interrupts. */
                push    _IEN0
-               clr     _EA
+               setb    _EA
                push    DPL
                push    DPH
                push    b
@@ -98,7 +98,7 @@ ao_yield(void) _naked
        if (ao_cur_task_id != AO_NO_TASK)
        {
                /* Save the current stack */
-               stack_len = SP - AO_STACK_START;
+               stack_len = SP - (AO_STACK_START - 1);
                ao_cur_task->stack_count = stack_len;
                stack_ptr = (uint8_t __data *) AO_STACK_START;
                save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
@@ -107,7 +107,7 @@ ao_yield(void) _naked
        }
        
        /* Empty the stack; might as well let interrupts have the whole thing */
-       SP = AO_STACK_START;
+       SP = AO_STACK_START - 1;
 
        /* Find a task to run. If there isn't any runnable task,
         * this loop will run forever, which is just fine
@@ -123,11 +123,12 @@ ao_yield(void) _naked
 
        /* Restore the old stack */
        stack_len = ao_cur_task->stack_count;
+       SP = AO_STACK_START - 1 + stack_len;
+
        stack_ptr = (uint8_t __data *) AO_STACK_START;
        save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
        while (stack_len--)
                *stack_ptr++ = *save_ptr++;
-       SP = (uint8_t) (stack_ptr - 1);
 
        _asm
                pop             _bp