Guralp Systems CMG-DM24 - Manual (Page 17)

Operator's guide
Instructs the DM24 to transmit any continuous streams directly to
clients as for DIRECT mode, but to store triggered data into Flash
storage as for FILING mode.
If you choose DUAL mode but do not select any continuous streams for
output, the instrument will send heartbeat messages as for FILING
mode. Scream! can pick these up and download new data as
necessary.
FIFO (First In First Out)
Command: FIFO
Instructs the DM24 to begin writing blocks to Flash memory as for
FILING mode, but also to transmit data to clients. Data is transmitted
in strict order, oldest first; the DM24 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 mode for each device (if applicable) to ensure that
data flow works the way you expect.
Like all the transmission modes, FIFO mode does not delete data once
it has 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 it is overwritten (in the RECYCLE buffering mode,
see below) or if you delete it manually.
ADAPTIVE
Command: ADAPTIVE
October 2009 17