Guralp Systems CMG-5TD User Manual
Page 27
Operation
5.9.5.5 FIFO (First In First Out)
Instructs the digitizer to begin writing blocks to Flash memory as for FILING
mode, but also to transmit data to clients. Data are transmitted in strict order,
oldest first; the digitizer will only transmit the next block when it receives an
explicit acknowledgement of the previous block.
If the communications link is only marginally faster than the data rate, it will
take some time to catch up with the real-time data after an outage. If you
want data to be transmitted in real-time where possible, but are worried about
possible breaks in communication, you should use ADAPTIVE mode instead.
FIFO mode will consider a data block successfully transmitted once it has
received an acknowledgement from the next device in the chain. If there are
several devices between you and the instrument, you will need to set up the
filing mode for each device (if applicable) to ensure that data flow works the
way you expect.
Like all the filing modes, FIFO mode does not delete data once they have been
transmitted. You can still request anything in the Flash memory using
Scream! or over the command line. The only way data can be deleted is if
they are overwritten (in the RECYCLE buffering mode, see below) or if you
delete them manually.
5.9.5.6 ADAPTIVE
Instructs the digitizer to transmit current blocks to clients if possible, but to
store all unacknowledged blocks in the Flash memory and re-send them,
oldest first, when time allows. ADAPTIVE mode is best suited for “real-time”
installations where the link between digitizer and client is intermittent or
difficult of access.
If the communications link is only marginally faster than the data rate, it will
usually be busy transmitting real-time data. Thus, it may take a while for the
instrument to work through the missed blocks. In this case, and if your client
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Issue D - April 2013