pSOSystem System Calls - Read

tm_tick pSOS+ System Calls
tm_tick Announces a clock tick to the pSOS+ kernel.
#include
unsigned long tm_tick()
Description
Return Value
Error Codes
Notes
This system call is used to inform the pSOS+ kernel of the arrival of a new clock
tick. The pSOS+ time manager uses it to update its time and date calendar, count
down tasks that are timing out, and track a running task's time-slice for roundrobin
scheduling. Normally, the user's real-time clock ISR calls tm_tick().
The frequency of tm_tick() calls is fixed and defined in the pSOS+ Configuration
Table as kc_ticks2sec. Thus, if the value is 100, the pSOS+ time manager
interprets 100 tm_tick() calls as one real-time second.
This call always returns 0.
None
1. tm_tick() is very fast: it just notifies the system of the arrival of another clock
tick. Most other Time Manager actions that can result from this clock tick are
postponed until the pSOS+ kernel dispatches and do not run at the clock
interrupt level. This improves deterministic system interrupt response.
2. The system accumulates announced ticks when necessary, so no chance exists
for an overrun or missed tick. Typically, the accumulation never counts past 1.
However, if a system contains one or more lengthy ISRs that respond to high
frequency interrupt sources, they can monopolize the CPU enough to prevent
the pSOS+ kernel from processing a tick before the next one arrives. In such
rare cases, the pSOS+ kernel accumulates the ticks for subsequent accounting.
Multiprocessor Considerations
None. This call can only be directed at the local processor node.
1-178 pSOSystem System Calls