Concurrent Technologies RCIM, User Manual

Page: 37 / 102

Functional Description
3-5
Synchronizing the Tick Clock
1
When the RCIM master system boots,
rcim_clocksync
is executed, which resets all
tick clocks in the RCIM chain to zero.
When an RCIM slave system boots after the master has booted, the tick clocks on the
systems in the RCIM chain will be out of sync, unless automatic clock synchronization is
configured (see the section “Automatic Synchronization” below). Invoking
rcim_clocksync
without options on the master RCIM system synchronizes all tick
clocks in the RCIM chain. See the section “The rcim_clocksync Utility” and the
rcim_clocksync(1)
man page for more information about this utility.
RCIM Masterclock Considerations
1
The RCIM POSIX clock is the system masterclock. This means that system time
continually looks at the RCIM's POSIX clock and adjusts itself to match.
In previous releases of RedHawk, a broken or stopped RCIM would confuse and often
lock up the system, however this is no longer the case. The RedHawk masterclock code
now continually tests the RCIM POSIX clock for validity and pauses clock
synchronization if problems are detected. This means that the two clocks, the RCIM
POSIX clock and the system clock, become free-running. Once the RCIM POSIX clock
again becomes valid clock synchronization is resumed.
In order for synchronization to resume, RedHawk must detect that both the system clock
and the RCIM POSIX clock are incrementing, that each clock is incrementing at the
correct rate, and that each clock has a value within approximately two seconds of the
other. This latter condition is most easily achieved by executing a
clock_settime
(3),
but other methods, as documented in
masterclock
(5), are available that may be more
suitable for specific situations.
Synchronizing the POSIX Clock
1
The POSIX clocks tick synchronously but generally do not have the same clock values and
should not be used as a common time stamp. They can be synchronized with the other
Status:
tick timer
posix clock
is one of the following:
CABLE_SYNC
– indicates that the RCIM slave clock is being driven by RCIM master cable clock signal, if
available
CABLE_ENABLE – indicates that the RCIM clock resets when RCIM master does a synchronization
LOCAL_ENABLE – indicates that the clock is enabled
NO_RESET_WHEN_DISABLED
– indicates that the clock is not reset when disabled
Values:
tick timer
posix clock
current clock values for each clock
o p e r a t i o n s
are:
This section is usage information for the interactive mode. At the
enter operation:
prompt, supply
one of the operation codes to accomplish the task described for that operation. As noted, some operations
require a designation for the clock to be operated on:
t for the tick clock; p for the POSIX clock.