AVR-Chat

>
>No, this is not true. My cooperative multi-tasking operating system, 
>ECROS (see http://ecros.ecrostech.com), includes an event mechanism. 
>There is no polling. When an event is sent to a task, the task is 
>queued for execution if that event causes its ready condition to be 
>satisfied. I suppose you could say that the queues are polled, but I 
>think this would be stretching the definition of polling a bit far.

Ok, so there is then a list of tasks that are ready to be executed, which you drop through. Eventually, you hit the end, and start over, or just sit in a loop waiting for more tasks to do?

How exactly do you "send" an event to a task?

In terms I'm familiar with (I'm an assembler kind of guy), I might be sending data to a UART.  

First, I'd check wether handshake allows anything to be sent.
sbis PORTA,HSIN
ret


Second, I'd check wether the UART is actively sending something.
SBIC Ser_Flags,SER_TX_Busy
ret


Third, I'd check wether there's anything in the serial out buffer, to send.
Point at buffer, call circ_get, returns carry set if nothing in the buffer, 
otherwise returns carry clear, and the next byte to send.
brcs to label with return

If all these tests pass, then I put the byte to send in a single SRAM location, set the baud rate timer (software UART) to a minimum interval to trigger a timer int, and exit.

The int then causes the start bit, data bits, and stop bit to be sent, then the uart is marked as "not busy".