Re: [EXTERNAL] Modbus and SScan acquisition synchronisation and timestamp query

[Ralph Lange via Tech-talk <tech-talk at aps.anl.gov>]

On Wed, 12 Aug 2026 at 14:44, Kasemir, Kay via Tech-talk <tech-talk at aps.anl.gov> wrote:

When I had N records that all read from the same device via SCAN=I/O Intr, I’ve set the “TPRO” flag and that way saw in which order they are processed. Then I added an FLNK from the one record processed last to the record or chain of records that should process next to use the information just read from the device.

That “works” as long as your device support always reads items from the device and then issues the I/O Intr updates of the associated records in the same order. This was the case for the specific device that I used, but isn’t generally given.

Careful:

If you activate the feature that allows multiple parallel callback threads (to increase throughput on multi-processor systems), the strict order of processing of "I/O Intr" records - with respect to the order in which processing has been requested - is not guaranteed.

Actually, it has never been promised - it just happened as a side effect of only a single thread processing all records from the priority-specific callback queue.

Cheers,
~Ralph