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vrf IO Instrument Manager IEEE488

Question asked by VRFuser on May 8, 2006
Latest reply on May 8, 2006 by VRFuser
Hi Doug,
 
It is working the way it is supposed to work.  Whenever a direct I/O block executes, it cannot make any assumptions on the state of the bus before it took control.  Even though this thread has concurrent reads of the instrument, there is no way of knowing if another VEE thread or even another program took control of the bus and changed addressing between transaction boxes.  Therefore, the only thing VEE can do is send a new addressing sequence.
 
In fact, if your DUT is having problems over GPIB on a readdressing sequence, it is because the DUT is violating IEEE-488.1.  488.1 states that sending or receiving address bytes will not affect the contents of the input or output buffers.  This is intended so that programs can interleave messages to different devices on the bus.  I don't have a copy of dot-1 with me right now, but if you write and ask, I would be happy to quote section and paragraph on that. 
 

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

 


  _____  

From: TEIGLAND,DOUG (A-ColSprings,ex1) [mailto:doug_teigland@agilent.com]
Sent: Monday, May 08, 2006 6:50 AM
To: VRF
Subject: [vrf] IO Instrument Manager IEEE488



Hello Forum readers,

 

I am looking at a new instrument and I see some disturbing IEEE488

behavior.  Each time a new Direct IO block does a READ it issues

another TALK command, see attached IO log.  The DUT is dropping

the next byte in response to the new TALK.  The returned string

should be of the format: 0x47 0x46 0x46 … .

In this example I am seeing 047 046 0x46 … .

I works OK if all the reads occur in the same Direct IO block.

 

Does anyone know the proper response to repeated TALKS?

 

Thanks,

 

Doug Teigland


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