Experimental Physics and
Industrial Control System

[email protected] (Peregrine McGehee) · Fri, 14 Aug 1998 13:46:13 -0600

For rates less than your vxWorks clock rate (default 60Hz) you can add 
periodic scan rates to EPICS by modifying menuScan.ascii as described in 
the IOC Applications Developers Guide. For R3.13 see Chapter 14. Database 
Scanning.

The caveat is that your specified scan rates in seconds should map to a 
integral number of clock ticks - otherwise you will not get the timing you 
expect.

I've routinely used 20Hz (.05 second) scan rates for servo loops. This 
would be implemented by adding the following to the menu(menuScan) 
definition:

menu(menuScan) {
	:
	choice(menuScan__5_second, ".05 second")
}

With a 60Hz vxWorks clock, this scan task gets processed once every 3 
ticks.

Aloha,
	Peregrine

Peregrine M. McGehee				[email protected]
LEDA Control System Project Engineer 		(505) 667-3273
Accelerator Controls & Automation Group 	Los Alamos National Laboratory

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System