Telit Wireless Solutions SL869-T User manual

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Components, units, or third-party products used in the product described herein are NOT
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This document describes the portion of the serial communications interface between the
SL869-T GNSS receiver module timing firmware and Host Processor software that is related
to the timing feature. The described interface is reserved for users authorized under a Telit
Non-Disclosure Agreement to use timing module firmware and is a supplement to other
SL869 software user guides.
This document is intended only for distribution to Telit employees and to SL869-T GNSS
timing module customers who have signed a Non-Disclosure Agreement (NDA) with Telit
Wireless.
For general contact, technical support, to report documentation errors and to order manuals,
contact Telit Technical Support Center (TTSC) at:
TS-[email protected]
TS-NORTHAMERIC[email protected]
TS-LATINAMERIC[email protected]
TS-[email protected]
Alternatively, use:
http://www.telit.com/en/products/technical-support-center/contact.php
For detailed information about where you can buy the Telit modules or for recommendations
on accessories and components visit:
http://www.telit.com
To register for product news and announcements or for product questions contact Telit
Technical Support Center (TTSC).
Our aim is to make this guide as helpful as possible. Keep us informed of your comments and
suggestions for improvements.
Telit appreciates feedback from the users of our information.

This document contains the following chapters (sample):
“Chapter 1: “Introduction” provides a scope for this document, target audience, contact and
support information, and text conventions.
“Chapter 2: “Communication Interface”gives an overview of the serial communications
interface.
“Chapter 3: “Commands Description”describes in detail each of the input commands related
to timing for the SL869-T.
“Chapter 4: “Messages Description”describes in detail each of the output messages related to
timing which are produced by the SL869-T.
“Chapter 5: “Document History” provides of the changes made to this User Guide.
Danger –This information MUST be followed or catastrophic equipment failure or bodily
injury may occur.
Caution or Warning –Alerts the user to important points about integrating the module, if
these points are not followed, the module and end user equipment may fail or malfunction.
Tip or Information –Provides advice and suggestions that may be useful when
integrating the module.
All dates are in ISO 8601 format, i.e. YYYY-MM-DD.
1. SL869 Product Description, 80405ST10105A
2. SL869 Software User Guide, 1VV0301002
3. SL869 Software Authorized User Guide, 1VV0301052

The SL869-T timing module is a member of the SL869 product family that is intended for use
in timing applications. The timing firmware within the module provides an accurate PPS
signal by holding an internal reference position that represents the location of the antenna for
the timing module, and then by applying satellite measurements only to the calculation of
time. Because the internal reference position is “held” by the module firmware, this timing
feature of the SL869-T is also known as Position Hold mode. While in Position Hold mode,
the SL869-T timing module firmware also performs time-receiver autonomous integrity
monitoring (T-RAIM) to ensure a high degree of integrity of the PPS signal. Position Hold
mode and the held internal reference position are maintained through commanded software
resets.
The serial communication interface between the SL869-T timing module and the Host
processor is based on the NMEA-0183 protocol standard. More information regarding the
NMEA protocol and its use by the SL869 module family can be found in Section 2 of the
Software Guides for public and authorized users listed as References in the Introduction
above. Note that the default settings for the serial communications port used by the SL869-T
timing firmware are:
115200 Baud
Eight data bits
No parity bits
One stop bit
The timing feature is managed using proprietary NMEA commands and messages. A
command interface allows the user to set and poll the internal reference position used for
Position Hold mode, as well to obtain information regarding the status of the T-RAIM
algorithm.
Unlike the standard SL869 module, by default the SL869-T timing module outputs a pulse
every second. It is able to output an accurate pulse with only one satellite in track when in
Position Hold mode.
As mentioned above, in Position Hold mode an internal reference position is held by the
SL869-T timing module firmware, which removes position uncertainty and allows the
firmware to apply satellite measurements exclusively to the calculation of time and the

production of an accurate PPS signal. The internal reference position can be established in a
number of ways.
The SL869-T timing module firmware includes an auto-survey algorithm that can determine
the reference position from a series of position fix samples. The factory default is for the
auto-survey algorithm to be enabled at start-up, whereby the module operates for at least one
hour (3600 position fixes) as a positioning receiver, after which it enters Position Hold mode
using the calculated reference position.
Commands to change the number of required samples or to disable the auto-survey algorithm
are provided and are described later in this document.
If the number of required samples is changed, or if the module is given any sort of
commanded software reset (e.g. a $PSTMHOT command) while the auto-survey algorithm is
underway, the algorithm is restarted.
If the antenna position is accurately known a priori when the SL869-T timing module is
installed, the module can be commanded into Position Hold mode and to specifiy the antenna
position as its held reference position. The module can also be configured via command to
start-up in Position Hold mode using the specified antenna position as its reference position.
Note that the auto-survey algorithm should be disabled when using a commanded reference
position.
The relevant commands are described later in this document.
It is important to note that the timing output is managed independently from the navigation
algorithm, and therefore the SL869-T timing module behaves as a positioning receiver even
while it is in Position Hold mode. Thus the reported position will reflect the antenna position
as if it were output by a standard SL869 module, which may or may not be the same as the
internally held reference position.