Opto 22

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KB53614
Data streaming synchronization to multiple hosts modified in SNAP PAC and Ultimate I/O controllers
Revision:  3.0
Published:  7/9/2007
Applies To
Firmware for:
SNAP-PAC-S1
SNAP-PAC-R1
SNAP-PAC-R2
SNAP-UP1-ADS
SNAP-UP1-M64
SNAP-UP1-D64
SNAP-LCE
Versions
Feature is changed beginning in version:  
R8.0a SNAP PAC firmware
Feature is changed beginning in version:  
R7.2d Ultimate I/O firmware

DESCRIPTION

If the streaming feature is configured to send to multiple stream clients, the synchronization code, an integer whose value is changed each time data is streamed, is incremented between each host, instead of after transmitting to all hosts.

For example,
    Send to Client 1: stream data x, sync code: 1
    Send to Client 2: stream data x, sync code: 2
    Send to Client 3: stream data x, sync code: 3
    Send to Client 1: stream data y, sync code: 4
    Send to Client 2: stream data y, sync code: 5
    Send to Client 3: stream data y, sync code: 6
    Send to Client 1: stream data z, sync code: 7
    Send to Client 2: stream data z, sync code: 8
    Send to Client 3: stream data z, sync code: 9
Client 1 receives packets with sync code 1, 4, and 7. With this behavior, the client cannot detect if stream packets are dropped.

RESOLUTION

Opto 22 has modified stream synchronization.

The streaming logic is changed so the synchronization code is incremented only after sending the stream packet to all clients:

    Send to Client 1: stream data x, sync code: 1
    Send to Client 2: stream data x, sync code: 1
    Send to Client 3: stream data x, sync code: 1
    Send to Client 1: stream data y, sync code: 2
    Send to Client 2: stream data y, sync code: 2
    Send to Client 3: stream data y, sync code: 2
    Send to Client 1: stream data z, sync code: 3
    Send to Client 2: stream data z, sync code: 3
    Send to Client 3: stream data z, sync code: 3
Client 1 receives packets with sync code 1, 2, and 3. With this behavior, each client can assume stream packet(s) were dropped if the synchronization code increases by more than one from one stream packet to the next.

Relevant Downloads
No relevant downloads have been specified.
Questions? Contact Opto 22 Product Support.
Phone: 800-835-6786 or 951-695-3080
Email: support@opto22.com

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This Opto 22 Knowledge Base ('OptoKB') article is intended to provide general technical information on a particular subject or subjects and is not an exhaustive treatment of such subjects. Accordingly, the information in this OptoKB article is not intended to constitute application, design, software, or other professional engineering advice or services. Opto 22 may modify the OptoKB articles at any time. Before making any decision or taking any action which might affect your equipment, you should consult a qualified professional.

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