Experimental Physics and
Industrial Control System

"[email protected]" <[email protected]> · Tue, 10 Jul 2018 09:36:08 +0000

> Here is a very curious issue that I've just stumbled across: asynchronous
> caput failure is reported, synchronous caput failure is hidden.

I have managed to pin this down a bit further by running wireshark with Michael Davidsaver's nice caproto plugin, and it appears that the IOC (not the client library) is responsible for hiding the synchronous caput failure.

Below is a transcript of two caput sessions.  In the first exchange we send CA_PROTO_WRITE and receive CA_PROTO_ERROR in response, in the second we send and receive CA_PROTO_WRITE_NOTIFY with ECA_NORMAL in the response.

This is tested with EPICS 3.14.12.3, so maybe this has been fixed in a more recent version, but given the cryptic character of this issue maybe not.

Asynchronous

Client -> IOC
    Command: Write (0x0004)
    Payload Size: 8
    DBR Type: DOUBLE (6)
    Data Count: 1
    Operation ID: 1
    Server Channel ID: 519
    Value: 0

IOC -> Client
    Command: Error (0x000b)
    Payload Size: 48
    Data Type: 0x0000
    Data Count: 0
    Client Channel ID: 1
    Status: ECA_PUTFAIL (0x000000a0)
    Channel Access
        Command: Write (0x0004)
        Payload Size: 8
        Data Type: 0x0006
        Data Count: 1
        Param 1: 0x00000207
        Param 2: 0x00000001
    Error Message: TS-DI-TMBF-02:MEM:CAPTURE_S

Synchronous

Client -> IOC
    Command: Write Notify (0x0013)
    Payload Size: 8
    DBR Type: DOUBLE (6)
    Data Count: 1
    Operation ID: 3
    Server Channel ID: 520
    Value: 0

IOC -> Client
    Command: Write Notify (0x0013)
    Payload Size: 0
    DBR Type: DOUBLE (6)
    Data Count: 1
    Operation ID: 3
    Status: ECA_NORMAL (0x00000001)

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System