Monitor the I/O system and detect channels or variables that are not being updated. This can be done using 5 different methods.

1) looking for a change in the raw data value which is supposed to be updated by the input driver

2) looking for a change in the engineering value of a variable which might be caused by the transfer layer or by a “node-linked” operation

3) looking for a minimum value of “noise” on a variable by monitoring the std deviation of a running average buffer

4) monitoring the “variable age” – the time since the variable was last updated by any process

5) using an event to trigger the actions – either a single occurrence of the event or a requirement that there must be more than one received within a certain time period

The processing of these methods is performed only if the expression on the first line of the specification file evaluates to TRUE.

For each method, an action can be specified to either perform a normal shutdown or an emergency shutdown if the channel/variable is evaluated as being “dead” for a specified period or the event’ has been received as specified. An additional delay can be specified to kill the cell “watchdog” circuit. A zero value for the watchdog delay specifies that the watchdog will not be killed.

The methods can be specified in a specification file, which must be /cell/dead_chan_specs. A maximum of 256 specifications is allowed.

An example is shown below:

 “if( key_switch &&  ( RPM > 150[rpm] ) ) then TRUE else FALSE”  
variable   eval_period type        action_type    watchdog_delay  
cmp_in_p    10[sec]     EU_COMP     ABORT          30[sec]  
cmp_ot_p    15[sec]     RAW_COMP    ABORT          30[sec]  
int_mnf_p   20[sec]     AGE_TEST    ABORT          10[sec]  
 or the following for a standard deviation evaluation  
variable   eval_period type        limit_value action_type   watchdog_delay  
blow_by     10[s]       SD_LIMIT    0.1[psi]    EMERGENCY     30[s]  
 or the following for an event  
event_name  eval_period   type     action_type    watchdog_delay  
ctd20_err    10[sec]      EVENT      ABORT         0[s]  


dead_channel &






This process is normally launched by the “sys_start” task and requires no command line arguments.
The specification file “/cell/dead_chan_specs” must exist else the process will terminate.
The process may be manually launched if it terminates when launched by “sys_start”.


See Also: