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SYS/BIOS On-Line Training
Introduction to Timers / Clocks
SYS/BIOS
1
SYS/BIOS Timing Services
• Timer Module
– Manages timer peripherals
– Provides target/device abstraction
• Clock Module
– Manages BIOS “heartbeat”
– Can schedule functions to fire in the future (one-shot or periodically)
– Input can be configured to use Timer module “tick” or application “tick”
• Timestamp Module
– Provides simple time stamping services for benchmarking code
– Allows time stamping RTA logs
2
BIOS Timer Architecture
Func1()
Application Software
Fired as One-Shot or Periodic
BIOS Software
ISR
BIOS Timer Module
Timer Peripheral
Timer Peripheral
Timer Peripheral
MSP430 Hardware
3
BIOS Timer/Clock Architecture
Func1()
Func2()
Func3()
Func4()
Application Software
Fired as One-Shot or Periodic
Swi_post()
Clock.doTick()
BIOS Clock Module
BIOS Software
ISR
BIOS Timer Module
Timer Peripheral
Timer Peripheral
Timer Peripheral
MSP430 Hardware
4
Controlling a Clock Function
Clock created and
started with startFlag
or Clock_start()
Func runs
One-shot Clock
timeout
Func runs
Continuous Clock
timeout
period
Func runs
period
Func runs
...
Time
• Clock_start(), Clock_stop(): Clock Instances can be stopped/restarted
– Can only be called from the context of the Clock Swi
• Clock_tickStart()/Clock_tickStop(): starts/stops the timer generating the
underlying timer tick
• Clock_setPeriod(), Clock_setTimeout(), Clock_setfunc(): Modifies a stopped
Clock instance
• Clock_tickReconfig allows Clock params to be reconfigured based on a new
timer frequency
5
Clock Run-Time API
Clock_Params clockParams;
Task_Handle myClock;
Error_block eb;
Clock_Params_init(&clockParams);
clockParams.period = 4;
/* every 4 Clock ticks */
clockParams.startFlag = TRUE; /* start immediately */
Error_init(&eb);
myClock = Clock_create((Clock_FuncPtr)clockHandler, 4, &clockParams, &eb);
Clock_create
Clock_delete
Clock_getTicks
Clock_getTimeout
Clock_getTimerHandle
Clock_Params_init
Clock_setFunc
Clock_setPeriod
Clock_setTimeout
Clock_start
Clock_stop
Clock_tick
Clock_tickReconfig
Clock_tickStart
Clock_tickStop
Allocate and initialize a new instance object and return its handle
Finalize and free this previously allocated instance object, setting the referenced
Time in Clock ticks
Get timeout of instance
Get timer Handle
Initialize this config-params structure with supplier-specified defaults before
Overwrite Clock function and arg
Set periodic interval
Set the initial timeout
Start instance
Stop instance
Function called by the timer isr when tickSource is TickSource_TIMER
Reconfigure clock for new cpu frequency
Start clock after reconfiguration
Stop clock for reconfiguration
6
Configuring the Clock Module with XGCONF
timerId: specify -1 to
request any timer
swiPriority: priority of
the clock functions
running periodically
(defaults to 15)
tickPeriod: specifies period
between system ticks
(defaults to 1000 usec)
tickSource:
• tickSource_TIMER: creates timer to generate
system tick (periodic call to Clock_tick)
• tickSource_USER: application calls Clock_tick
from a user interrupt
• tickSource_NULL: no APIs with a timeout value
and no Clock APIs.
7
*
Adding a Clock Object With XGCONF
clockfxn: function to
be called
timeout: initial period
period: sets subsequent
timeout interval (in Clock
ticks). One-shot => set to 0.
startFlag:
• true => starts immediately
• false => starts on call to
Clock_start()
arg: argument to clockFxn
8
*