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Can the TNT4882 Chip Lose Data During a Device Clear (DCL) or Interface Clear (IFC)?

Hardware: GPIB

Problem:
Can the TNT4882 chip lose data during a device clear (DCL) or interface clear (IFC)?

Solution:
If you follow the IEEE 488.2 specification, you should never lose any data bytes during a device clear or an interface clear. If you write your interrupt handler (more probable in non-interrupt, polling mode) to read the status registers and process them in this order:

1. if LACS setup TNTio
   
2. if IFC clear interface
   
3. if DCAS clear interface
   
4. if TACS setup to talk

What could happen is that if IFC or DCAS is followed by DABs, then the software will start to read the data after the IFC occurs, but before the software processes the IFC!

So by swapping the code steps around like this:

1. if IFC clear interface
   
2. if DCAS clear interface
   
3. if LACS setup TNTio
   
4. if TACS setup to talk

you will be able to successfully clear the interface before you read any data bytes.

Related Links:
KnowledgeBase 2BCCC3XY: Can I Still Receive Data from the TNT4882 ASIC If My Controller Does Not Toggle the NRFD Handshake Line?
Product Manual: TNT4882 Programmer Reference Manual

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Report Date: 08/26/1998
Last Updated: 04/02/2008
Document ID: 1CPAOTQA

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