RE: state notation code flags

["Mark Rivers" <rivers@cars.uchicago.edu>]

OK, I was not aware that doing a pvGet on a PV that you have set a monitor and event flag on would set the event flag.  But you normally would never do this: if you set a monitor on a PV then you don't ever need to do a pvGet on it; the variable is guaranteed to always contain the most recent value of that PV without ever calling pvGet.
 
Mark
 

________________________________

From: Patrick Thomas [mailto:thomas_p@ligo-wa.caltech.edu]
Sent: Fri 10/2/2009 7:29 PM
To: Mark Rivers
Cc: tech-talk@aps.anl.gov
Subject: Re: state notation code flags



This also prints out the flag:

program sncTest

float test_put;
assign test_put to "H3:TEST_PUT";
monitor test_put;
evflag test_putEvent;
sync test_put test_putEvent;

float test_get;
assign test_get to "H3:TEST_GET";
monitor test_get;
evflag test_getEvent;
sync test_get test_getEvent;

ss ss1 {
        state init {
                when () {
                        efClear(test_getEvent);
                        pvGet(test_get);
                        if (efTest(test_getEvent)) {
                                printf("flag set\n");
                        }
                } state wait

/*
                when () {
                        efClear(test_putEvent);

                        test_put = 40;
                        pvPut(test_put, SYNC);
                        efClear(test_putEvent);
                } state wait
*/
        }

        state wait {
/*
                when () {
                        if (efTest(test_putEvent)) {
                                printf("flag set\n");
                        }
                } state wait
*/
                when () {
                } state wait
        }
}



Mark Rivers wrote:
> Patrick,
>
> pvGet will not set the event flag.  Event flags are only set on monitor
> callbacks, i.e. when the value changes in the IOC and it does callbacks
> to channel access clients that have subscribed to that channel.
>
> pvGet(pv) normally blocks for the operation to complete, so it gives the
> same behavior as pvGet(pv, SYNC) (unless you compiled with the +a
> option, which I would not recommend).
>
> pvPut(pv) and pvPut(pv, SYNC) do behave differently, because the default
> behavior is not to wait for the pvPut to complete, adding the SYNC
> option forces it to wait for the put to complete.
>
> Mark
>
>
> -----Original Message-----
> From: Patrick Thomas [mailto:thomas_p@ligo-wa.caltech.edu]
> Sent: Friday, October 02, 2009 1:25 PM
> To: Mark Rivers
> Cc: tech-talk@aps.anl.gov
> Subject: Re: state notation code flags
>
> Hi Mark,
>
> If I have the following:
>
> float request_move_to_absolute_position;
> assign request_move_to_absolute_position to
> "{IFO}:{DRIVER}_REQUEST_MOVE_TO_ABS_POS_{AXIS}";
> monitor request_move_to_absolute_position;
> evflag request_move_to_absolute_positionEvent;
> sync request_move_to_absolute_position
> request_move_to_absolute_positionEvent;
>
> ...
>
> pvGet(request_move_to_absolute_position);
> efClear(request_move_to_absolute_positionEvent);
>
> Will the pvGet set the request_move_to_absolute_positionEvent flag? If
> so, is it possible that even with the efClear, the flag will remain set
> at the end of the code, because the pvGet will not have completed before
>
> the efClear is encountered? But if
> pvGet(request_move_to_absolute_position, SYNC) is used, will this
> guarantee that the efClear will clear the flag?
>
> Thank you,
> Patrick
>
>
> Mark Rivers wrote:
>  
>> Patrick,
>>
>> Event flags can be explicitly set, which is typically used to allow
>> communication between state sets.  Or event flags can be synced to a
>>    
> PV,
>  
>> and will be set whenever a monitor is received for that PV, as in the
>> example I sent you.
>>
>> You can use the efTest() function outside of a when statement, just
>>    
> like
>  
>> any other function.
>>
>> Mark
>>
>>
>> -----Original Message-----
>> From: Patrick Thomas [mailto:thomas_p@ligo-wa.caltech.edu]
>> Sent: Thursday, October 01, 2009 5:20 PM
>> To: Mark Rivers
>> Cc: tech-talk@aps.anl.gov
>> Subject: Re: state notation code flags
>>
>> Hi Mark,
>>
>> Are the flags on a monitored variable set whenever the monitored
>> variable is used in the code, including a pvPut, pvGet, assignment,
>> calculation, or print statement? Is there a way to test if the flag is
>>    
>
>  
>> set besides an efTest in a when statement?
>>
>> Thank you,
>> Patrick
>>
>> Mark Rivers wrote:
>>  
>>    
>>> Hio Patrick,
>>>
>>> Here are some code snippets from one of my SNL programs.  It has a
>>>    
>>>      
>> variable nelements assigned to a PV, and a monitor on that PV.  It has
>> an event flag, nelementsMon that is synced to nelements.  Whenever
>> nelements changes the event flag will be set.  In the init state I
>>    
> clear
>  
>> the event flag, just to be sure it is clear when the SNL code starts
>> running (after all PVs connect).  I then use efTestAndClear in a when
>> statement to take actions when that event flag is set, and to clear
>>    
> it.
>  
>> This works fine for me.
>>  
>>    
>>> int     nelements;   assign nelements    to "{P}{R}Nelements.VAL";
>>> monitor nelements;
>>> evflag nelementsMon;    sync nelements  nelementsMon;
>>>
>>>
>>>     /* Initialize things when first starting */
>>>     state init {
>>>         when() {
>>>             /* Clear all event flags */
>>> ...
>>>
>>>             efClear(nelementsMon);
>>>         } state monitor_inputs
>>>     }
>>>
>>>
>>> ...
>>>
>>>     state monitor_inputs {
>>>
>>> ...
>>>
>>>         when(efTestAndClear(nelementsMon) && (nelements>=1)) {
>>>             /* If nelements changes, then change endPulses to this
>>>    
>>>      
>> value,
>>  
>>    
>>>              * since this is what the user normally wants.  endPulses
>>>    
>>>      
>> can be
>>  
>>    
>>>              * changed again after changing nelements if this is
>>>    
>>>      
>> desired. */
>>  
>>    
>>>             if (moveMode == MOVE_MODE_RELATIVE)
>>>                 endPulses = nelements;
>>>             else
>>>                 endPulses = nelements-1;
>>>             pvPut(endPulses);
>>>         } state monitor_inputs
>>>     }
>>>
>>> Mark
>>>
>>> ________________________________
>>>
>>> From: tech-talk-bounces@aps.anl.gov on behalf of Patrick Thomas
>>> Sent: Wed 9/30/2009 10:35 PM
>>> To: tech-talk@aps.anl.gov
>>> Subject: state notation code flags
>>>
>>>
>>>
>>> Hi,
>>>
>>> I was wondering if there is a way to track at what point in the state
>>> notation code evflags are getting set and cleared, or if someone
>>>      
> could
>  
>>> clarify under what conditions they get set. I'm having trouble with
>>>    
>>>      
>> them
>>  
>>    
>>> getting set somewhere and not being cleared, but I'm not sure where.
>>>
>>> Thank you,
>>> Patrick
>>>
>>>
>>>  
>>>    
>>>      
>>  
>>    
>
>