Experimental Physics and
Industrial Control System

Kate Feng <[email protected]> · Fri, 08 Sep 2006 12:07:53 -0400

Andrew Johnson wrote:

> Kate Feng wrote:
> > For those applications, it seems that the overhead for the
> > VME read/write is necessary to be considered only inside
> > the related ISRs or in the related non-ISR routines where
> > the interrupt has to be disabled, which is rare.
>
> Actually I don't think it's that rare.  I have counted something like 30
> calls to the vxWorks intLock() routine in our R3.13.10 support module
> area, most of which are protecting code that manipulates at least one
> card register over the VMEbus while the lock is held.

OK, it's  my mistake to add "which is rare".

> In addition I
> counted 79 calls to intConnect(), and most of those ISRs will be
> manipulating VME card registers.
>
> Every one of those drivers must be examined and may have to be modified
> if we decide to use a Tempe-based CPU board here.  That's a lot of work!
>
> The PCIbus Retry and Disconnect cycle terminations that you discussed do
> not actually stop the data transfer cycle completely, they only permit
> it to be run again or to take longer to complete than a regular PCIbus
> single I/O cycle.
>

Yes, that's why the overhead is only needed for ISR and where interrupt is
disabled.
It was only a technical statement.  It does not imply any project cost
decision
or the amount of work needed.

Kate

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System