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vrf GPIB question...

Question asked by VRFuser on Sep 7, 2006
  • Comment • 9
OK, I am picking a nit here, but it is an important one.
 
Only one device in a system can be system controller.  The SYSTEM controller is never passed.  ACTIVE control can be passed.  This grants permission for the active controller to assert the ATN line.  However, the system controller retains control of the interface clear hardware line, and I believe also the REN line (remote).  Asserting the ifc line will clear bus traffic, but will also return active control to the system controller.
 
If there are two active controllers you find that one is constantly driving the ATN low and the other attempting to drive it high.  This causes current flow that can potentially damage cards, and will definitely cause unreliable bus traffic.  Whether it works will depend on a lot of factors like relative cable length and the number of devices loading the bus. 
 
Short answer, don't do it.
 
However, back in the day we used to simply turn off the controller we weren't using.  A GPIB system will work if at least 1/2 of the devices connected are powered up.  We also used to violate the total length and the having a load every meter rules as well.  The 16 max devices was a hard rule though and attempts to exceed that would cause the bus to fail.
 

Jay Nemeth-Johannes 
Smart Sensor Systems 
720 SW 14th Street
Loveland, Colorado 80537
(970) 663-0006  (Office)
(970) 290-9797 (Cell)
HYPERLINK "http://www.smartsensorsystems.com/"www.SmartSensorSystems.com

 


  _____  

From: Street, Andy M [mailto:andy.street@tycoelectronics.com]
Sent: Thursday, September 07, 2006 6:28 AM
To: VRF
Subject: RE: [vrf] GPIB question...


Hi Doug et al,
 
Warren is correct - only one person can be the boss at any given time.  In others words, GPIB only allows for one system controller at a given instant.  I am not too sure what your ultimate goal is with all of this, but it may be worthwhile considering GPIB via LAN.  Either use a dedicated GPIB/LAN box such as an E5810 or use a PC equipped with a GPIB interface and configure as a LAN server (this could be the existing PC).  Basically your laptop (hooked to the PC with the GPIB resource via LAN) and the PC itself use the same GPIB resource.  Issue is that you will have to manage any contention i.e. you want to control instruments whilst the script is doing stuff with them.  GPIB-LAN server has been available in IO libraries for a long time. 
 
Andy

  _____  

From: Pickles, Warren [mailto:Warren.Pickles@tycoelectronics.com]
Sent: Thursday, September 07, 2006 3:17 AM
To: VRF
Subject: RE: [vrf] GPIB question...


Doug,
 
I've never done anything like that, but I think this is how it's done:  Only one device on the GPIB can be the controller; usually this is a PC sending commands to instruments.  To do what you want to do, you have to pass control between the two PCs.  You need to know the GPIB addresses of the two PCs (they must be different), and then you execute a pass_control command from the controller PC to the other PC.  From VEE you do this with I/O, Advanced I/O, Interface Operations, then configure a transaction appropriately. 
 
Regards,
Warren


  _____  

From: Douglas Rudrow [mailto:drudrow@Aurora.com]
Sent: 06 September 2006 23:01
To: VRF
Subject: [vrf] GPIB question...



Greetings All,

 

A question about control over the GPIB. We have A PC controlling a test system; it’s running some kind of scripting language. We would like to hook up another computer, let’s say my laptop, to control the same instruments. Is there any way to do this without disconnecting the first PC from the GPIB? I stopped the program and exited the application on the first PC, but somehow it doesn’t seem to relinquish control over the bus. I’ve gotten around this in the past with a GPIB switch, but I was wondering if there was some other way.

 

Thanks in advance,

Doug

 

Douglas B. Rudrow

Systems Development Lab Technologist

Aurora Networks

2803 Mission College Blvd.

Santa Clara, California, 95054

U.S.A.

(408) 235-7000 Main

(408) 235 7084 Direct

HYPERLINK "mailto:rvilla@aurora.com"drudrow@aurora.com

 


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