Keil rtos rtx full timing is not allowed ???

# Pragma large # include "stc12c5a. h # include <rtx51.h> // RTX-51 definitionssbit sound = P2 ^ 3; sbit sound1 = P2 ^ 4; sbit sound2 = P2 ^ 5; void producertask (void) _ task _ 0 {OS _set_slice (1000); // 12 MHz 1 ms OS _create_task (1); // create the consumer-task OS _create_task (2); OS _create_task (3 ); OS _delete_task (0);} void task1 (void) _ task _ partition priority _ 1 {While (1) // endless loop {OS _wait (k_tmo, 5, 0); sound1 = ~ Sound1 ;}} void task2 (void) _ task _ 2 _ priority _ 1 {While (1) // endless loop {OS _wait (k_tmo, 10, 0); sound2 = ~ Sound2 ;}} void task3 (void) _ task _ 3 _ priority _ 1 {While (1) // endless loop {OS _wait (k_tmo, 1, 0); sound = ~ Sound ;}} void main (void) {signed Char rtxreturnstate; rtxreturnstate = OS _start_system (0 );}
We can see from the sound waveform that it is inaccurate.