Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Fri, 10 Dec 2004 12:49:26 +0100

On Thursday 09 December 2004 20:20, Russell  Redman wrote:
> A really
> thorny problem arises for output records whose values are read back
> from the hardware in groups.  Status words are often of this kind,
> and I have several examples in my IOC of CAN messages that return
> four real values as 12-bit integers for the last-set values of a
> collection of DACs.  This is hard enough to deal with using ai 
> records in ³I/O Intr² mode, where the logic in simulation mode is
> utterly, utterly different from what happens in hardware mode.  It
> will be much worse for ao records during iocInit, which will not be
> configures for SCAN=²I/O Intr²..  I do not have a solution for this,
> except to disable the read-during-initialization for such records.

Some time ago I wrote a hardware record (called "hwLowcal", "lowcal' 
being our CAN bus protocol), and a special device support for the 
'real' records (ai,ao,bi, bo,...) so that their INP/OUT links point to 
the 8 input or output fields of the hardware records (this is called 
"devHwClient"). These INP and OUT links are asynchronous and 
bidirectional and thus support (asynchronous) warm reboot, I/O Intr 
scanning, grouped variables (8 bytes or 4 shorts or ...), etc. (Not 
simulation mode, although this could be added). The implementation is 
somewhat dirty, because it depends on some EPICS (3.13) internals. All 
this stuff is (an optional) part of our MultiCAN package.

Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System