Guralp Systems CMG-DCM build <10,000 - Manual (Page 196)

CMG-EAM (Platinum Firmware)
14.2.3 USB operations
The Authenticated Digitiser can behave as a USB storage device (via
the GPIO connector) or as a USB host (via the USB connector).
14.2.3.1 USB device mode
The Authenticated Digitiser is fitted with an internal Flash memory
device which is accessible via USB. It can be written to by selecting
“Internal USB storage” from the “Recording destination” drop-down
menu on the “Disk recording” menu (see section 10.2 on page 109).
When a USB host, such as a laptop or PC, is connected to the GPIO
port (who's pin-out is given in section 14.3.6 on page 203) internal
circuitry detects the USB power and automatically connects the Flash
memory to the USB socket, causing it to behave identically to a
standard USB memory stick.
When no power is detected at the USB port, the Flash memory is
available to the system as if it were a standard removable disk. All of
the disk recording options described in section 10.2 (on page 109) will
apply to this device.
196 Issue C
Note: Software developers working with GCF packets can
decode the selected gain setting from the GCF header as follows:
If the most significant bit of the System ID is zero, variable gain
is not used. If the most significant two bits of the System ID are
10 or 11, the next three bits encode the gain, using this code:
Bits 2, 3 & 4 Gain
000 not fitted
001 ×1
010 ×2
011 ×4
100 ×8
101 ×16
110 ×32
111 ×64