Experimental Physics and Industrial Control System
Dear Fellow Tech Talkers,
We have had some customers reporting problems with Hytec IP Cards when
used on the Acromag 9670, such a combination producing the continual
error....
Interrupt: uninitialized vme interrupt 255
Interrupt: uninitialized vme interrupt 255
Interrupt: uninitialized vme interrupt 255
Interrupt: uninitialized vme interrupt 255
Interrupt: uninitialized vme interrupt 255
......
Careful analysis here has discovered that the correct interrupt vector
is initially put out and serviced for one interrupt cycle, but then the
Acromag 9670 continues to generate interrupts even though there is no
interrupt source. Since there is no interrupt source there is no
interrupt vector and the default 255 is read.
The default acromag 9670 setup leaves it without its Auto Clear
Interrupts Enabled, where as the Hytec 8002 default is to only generate
an interrupt whilst an interrupt source exists. All the Hytec IP Cards
were written expecting this behaviour.
The Acromag Manual in its "Generic Interrupt Handler Actions" section
recommends a rather fiddly and lengthy way for the IP Cards ISR to clear
not only its own interrupt source but then also clear the 9670s.
There is a simpler fix, which is to enable the 9670's Auto Clear
Interrupt (i.e. set bit D7 in the Acromag 9670 Carrier Board Status
Register).
This fix should probably still work with other IP Cards, even if they
follow the alternative "Generic Interrupt Handler Actions" described on
page 11 of the Acromag manual is enacted, the carrier interrupt is
effectively disabled twice.
Auto Clearing the Interrupt considerably reduces the ISR Loading and
eases the IP Code, so I am surprised it is not the default for 9670 /
drivers.
I hope this information is of some help to anyone struggling with the
9670.
Regards
Darrell Nineham
Hytec Electronics Ltd.
Tel: +44 (0) 118 975 7770
Fax: +44 (0) 118 975 7566
Web: www.hytec-electronics.co.uk
Incorporated in England No 1246940
VAT NO GB 285 2479 27
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