Guralp Systems CMG-DM24S12AMS - Manual (Page 54)

CMG-DM24S12AMS Operator's guide
GPS data, including position, date/time and device status, is output in
NMEA format at 4800 baud once per second. A time synchronisation
pulse of 100 ms duration is output at 1 pps (pulse per second). Both
outputs use RS232 (or, optionally, RS422) line drivers, enabling you to
use cables up to 100 metres long.
For information on how to set up a GPS receiver, see Section 3.6, “GPS” .
USB to RS232 converter
Digital channels within the DM24S12AMS (the digital outputs of the
two internal digitisers, and the six DIGITAL A − F are carried over RS232
links to an 8-port EdgePort module, which allows the serial ports to be
emulated over USB. The PC is configured so that the external DIGITAL
A − F ports appear as if they were directly attached, together with two
Com ports for the internal digitisers.
If your installation requires some other setup of the PC's Com ports, you
can configure the EdgePort device using the driver software provided.
Further information can be obtained at the EdgePort documentation
website, http://www.ionetworks.com/support/epdocs.html
4.2 Inside the DM24
Internally, all DM24 digitisers are structured as shown in the diagram
overleaf, where each box represents a separate printed circuit board
within the module. There are two of these modules in the DM24S12AMS
unit, which operate separately.
The system is designed around a low power, high performance Hitachi
H8/500 microprocessor. This is a 16-bit processor with a large address
space for data storage and manipulation—1Mb in sixteen 64k pages. It
also includes many integrated functions such as multiple timers and
serial I/O ports. In addition, the system contains a Crystal
Semiconductor CS5321/2 chipset and Motorola 56002 DSP. The CS5321/2
provides data at 2,000 samples per second, triggered by the H8 timing
system, to the 56002 DSP. The DSP can control from 1 to 3 ADCs and
process the data.
54 Issue B