At the top of page 141 in the ATMEGA spec book it says that the internal
timers run off the system clock. In the mica2 case this is the 7.3728MHz
xtal on the last page of the schematic. According to the comments in the
code you reference they use a /8 pre-scaler, which means that the sysclock
is divided by 8 before going to the timer, and the comment says this is:
"921.6 KHz on MICA2".
Not that one should believe everything one reads in TOS code, but this
would indicate the resolution to be just over 1 microsec.
One day soon I need to systematically dig through the timer section of
the controller, which has to be one of the most confusing since it is
a 'do everything for everyone' module. But from cursory examination
I believe the above to be true...
MS
Sharmistha Maitra wrote:
Hello,
This is a question to the authors of FTSP and the people who have worked
with TIMERS on MICA2 mote.
The time synchronization protcol FTSP uses SystimeM.nc (in
tos/platform/mica2) as the timer for its protocol (for example
timestamping messages etc) . Reading the code, it seems that
SysTimeM.nc uses the 16-bit TIMER3 that is available on the Mica2
platform.
I want to know the frequency of this timer. In the ATMEGA128L datasheet
I could not find it. Also what is the purpose of the 1/8 prescaler in
SysTimeM.nc, if anybody can let me know.
I know this maybe a basic question but pleasebe patient with me.
Thanks very much,
Smaitra.
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