Guralp Systems Limited
MAN-T60-0002 - 6TD Operator's Guide

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1. Preliminary Notes 2. Introduction 3. First encounters 4. Installing the 6TD 5. Accessing data 6. Configuration with Scream! 7. Calibrating the 6TD 8. Command-line interface 9. Updating the 6TD firmware 10. Connector pin-outs 11. Specifications 12. Revision history

Section Index: 5.1. Receiving data in Scream! 5.2. Downloading data over FireWire 5.3. Reading 6TD disks 5.4. Downloading recorded data over the serial port or Ethernet interface

Chapter 5. Accessing data

The 6TD has six different transmission modes, which control whether the instrument transmits data via the serial port or network interface, stores data into its flash memory or some combination of both. Tranmission modes are described in section 6.2.5.

If you choose a transmission mode where data are transmitted in real time, you can receive the data using Güralp Systems’ free Scream! software or using a Güralp EAM, Güralp NAM or similar data acquisition system.

If you choose a transmission mode where data are stored in Flash memory, you can recover these data at a later date, using either the FireWire interface or a serial link.

Note: The FireWire interface is very much faster than the serial link: the serial link is intended for real-time data transmission. If you wish to retrieve recorded data, the serial link (and the Ethernet link, if fitted) are only really useful for small, ad-hoc transfers.

The Flash memory is used as a ring buffer. Two pointers into the memory keep track of where data were last read (the “Read Pointer”) and last written (the “Write pointer”). When either pointer reaches the end of physical memory, it wraps round back to the beginning. The behaviour of the recording system when the write pointer reaches the read pointer (i.e. when the memory becomes full of data, none of which have been downloaded) is governed by the commands RE-USE/RECYCLE and WRITE-ONCE, as described in section 6.2.6.

The rest of Chapter 5 describes:

5.1 Receiving data in Scream!

Note: The Scream! software is available free of charge. Scream is available for both Windows and Linux computers. To request a copy, please send an email to scream@guralp.com stating your name, any organisational affiliation, the equipment with which you are working and the nature of your work.

There are several ways in which a 6TD instrument can connect to Scream!:

To connect to a 6TD over the network:

5.2 Downloading data over FireWire

The easiest way to download data over Firewire is to connect a suitable disk to the FireWire port of the 6TD and power cycle the instrument.

Note: The 6TD requires the disk to be in DFD format. If the disk has not previously been used with a 6TD (or 3ESPCD), it must first be initialised: see section 8.8.13 for details. Once initialised the first time, it can then be reinitialised in the same way or, from within Scream, by selecting File → Reset SCSI disk... from the main menu

If you have ordered a 6TD with the powered FireWire option, you can attach the disk directly to the 6TD with no additional connections. Otherwise, you will need to connect the disk to a power source through the supplied adapter.

When the sensor restarts, it will automatically the disk and flush all new data to it.

If you do not want to restart the instrument, you can also flush data to disk manually:

5.3 Reading 6TD disks

The 6TD uses a special disk format, DFD, for recording data. This format is also used by other Güralp digitisers such as the DM24.

You can read this data into a PC using Scream! or the gcfxtract utility, which are freely available from the Güralp Systems Web site.

Note: The DFD format is not the same as that used by the Güralp Systems EAM data module, which uses an ext3, ext4 or a FAT32-compatible journalling file system.

Güralp Systems can provide fully-tested disks with FireWire and USB connectors. Alternatively, a third-party FireWire disk may be used (although compatibility is not guaranteed).

To read a disk using gcfxtract:

You can also read disks with Scream!. This allows you to view data in the process of being transferred, but is slightly slower, because Scream! does not read data in strict order. To read a disk with Scream!:

5.4 Downloading recorded data over the serial port or Ethernet interface

Note: This technique is not recommended for transferring significant quantities of data, due to the speed limitation. The FireWire interface should be used for this purpose: see section 5.2.

Start by configuring Scream to record all incoming data by visiting the “Recording” tab of the File→Setup dialogue:

Ensure that the first four check-boxes are ticked. Next, switch to the “Files” tab and choose an appropriate base directory, file format and filename format.

Click to save your changes and close the dialogue.

Next, open a connection to the digitiser's console. To do this using Güralp Systems' Scream! software, right-click on the digitiser's icon () and select Terminal…. From a Güralp EAM, issue the command

data-terminal

and select the appropriate data source from the menu.

To simply download all data held in the Flash memory, issue the command

ALL-FLASH ALL-DATA DOWNLOAD

followed by

GO

This will initiate a complete download. The ALL-FLASH and ALL-DATA commands act as modifers to tell the system whhat to download.

If you wish to download only a subset of data, you can replace the ALL-FLASH and ALL-DATA modifiers with other modifers to select different streams and/or time periods:

The parameters are illustrated in the diagram below. If you miss out a parameter, DOWNLOAD will re-use the value you last specified.

Note: You can pause a download by entering terminal mode, and either restart with another GO or abort with END-DOWNLOAD.

When you complete a DOWNLOAD without specifying a time period, the CD24 adjusts the internal read pointer to mark the latest position. This is then used as the start point for the next DOWNLOAD with the command ALL-TIMES.

The various modifiers are are summarised below and described in detail in section 8.8.

The DOWNLOAD command returns immediately, so that you can issue more commands if required. To close the connection and begin downloading with the specified selectors, issue the GO command.

Once the GO command has been issued, the window may close, depending on which emulator you are using. On an EAM, the data-terminal (minicom) session is closed by keying +, then .

PreviousNext

1. Preliminary Notes 2. Introduction 3. First encounters 4. Installing the 6TD 5. Accessing data 6. Configuration with Scream! 7. Calibrating the 6TD 8. Command-line interface 9. Updating the 6TD firmware 10. Connector pin-outs 11. Specifications 12. Revision history