Hi Antony:
The default system tick in MQX is 5ms. This is the smallest unit of the time that clocks the scheduler.
It is not possible to have a delay shorter than 5 milliseconds without modifying the BSP. Each BSP can have a different value in the Macro "#define BSP_ALARM_FREQUENCY 200". This macro defines the number of ticks per second. This means each tick is 5 milliseconds.
time_delay is for some time sensitive situation, if you need precise time, you can use hardware timer. I attached a document to describer its usage.
Have a nice day!
Regards
Daniel