Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Fri, 2 Oct 2009 16:45:26 -0500

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:[email protected]] 
Sent: Friday, October 02, 2009 1:25 PM
To: Mark Rivers
Cc: [email protected]
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:[email protected]] 
> Sent: Thursday, October 01, 2009 5:20 PM
> To: Mark Rivers
> Cc: [email protected]
> 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: [email protected] on behalf of Patrick Thomas
>> Sent: Wed 9/30/2009 10:35 PM
>> To: [email protected]
>> 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
>>
>>
>>   
>>     
>
>   

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System