Telit Wireless Solutions JF2 Installation manual

JF2
Hardware User Guide
1vv0300985 Rev.5
2018-05-04

JF2 Hardware User Guide Notices
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SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE
NOTICES
While reasonable efforts have been made to ensure the accuracy of this document, Telit assumes
no liability resulting from any inaccuracies or omissions in this document, or from use of the
information obtained herein. The information in this document has been carefully checked and is
believed to be reliable, however no responsibility is assumed for inaccuracies or omissions. Telit
reserves the right to make changes to any products described herein and reserves the right to
revise this document and to make changes from time to time in content hereof with no obligation to
notify any person of revisions or changes. Telit does not assume any liability arising out of the
application or use of any product, software, or circuit described herein; neither does it convey
license under its patent rights or the rights of others.
It is possible that this publication may contain references to, or information about Telit products
(machines and programs), programming, or services that are not announced in your country. Such
references or information must not be construed to mean that Telit intends to announce such Telit
products, programming, or services in your country.
COPYRIGHTS
This manual and the Telit products described herein may be, include or describe copyrighted Telit
material, such as computer programs stored in semiconductor memories or other media. Laws in
the Italy and other countries preserve for Telit and its licensors certain exclusive rights for
copyrighted material, including the exclusive right to copy, reproduce in any form, distribute and
make derivative works of the copyrighted material. Accordingly, any copyrighted material of Telit
and its licensors contained herein or in the Telit products described in this manual may not be
copied, reproduced, distributed, merged or modified in any manner without the express written
permission of Telit. Furthermore, the purchase of Telit products shall not be deemed to grant either
directly or by implication, estoppel, or otherwise, any license under the copyrights, patents or patent
applications of Telit, as arises by operation of law in the sale of a product.
COMPUTER SOFTWARE COPYRIGHTS
The Telit and Third Party supplied Software (SW) products described in this instruction manual
may include copyrighted Telit and other Third Party supplied computer programs stored in
semiconductor memories or other media. Laws in the Italy and other countries preserve for Telit
and other Third Party supplied SW certain exclusive rights for copyrighted computer programs,
including the exclusive right to copy or reproduce in any form the copyrighted computer program.
Accordingly, any copyrighted Telit or other Third Party supplied SW computer programs contained
in the Telit products described in this manual may not be copied (reverse engineered) or
reproduced in any manner without the express written permission of Telit or the Third Party SW
supplier. Furthermore, the purchase of Telit products shall not be deemed to grant either directly
or by implication, estoppel, or otherwise, any license under the copyrights, patents or patent
applications of Telit or other Third Party supplied SW, except for the normal non-exclusive, royalty-
free license to use that arises by operation of law in the sale of a product.

JF2 Hardware User Guide Notices
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USAGE AND DISCLOSURE RESTRICTIONS
I. License Agreements
The software described in this document is the property of Telit and its licensors. It is furnished by
express license agreement only and may be used only in accordance with the terms of such an
agreement.
II. Copyrighted Materials
Software and documentation are copyrighted materials. Making unauthorized copies is prohibited
by law. No part of the software or documentation may be reproduced, transmitted, transcribed,
stored in a retrieval system, or translated into any language or computer language, in any form or
by any means, without prior written permission of Telit
III. High Risk Materials
Components, units, or third-party products used in the product described herein are NOT fault-
tolerant and are NOT designed, manufactured, or intended for use as on-line control equipment in
the following hazardous environments requiring fail-safe controls: the operation of Nuclear
Facilities, Aircraft Navigation or Aircraft Communication Systems, Air Traffic Control, Life Support,
or Weapons Systems (High Risk Activities"). Telit and its supplier(s) specifically disclaim any
expressed or implied warranty of fitness for such High Risk Activities.
IV. Trademarks
TELIT and the Stylized T Logo are registered in the Trademark Office. All other product or service
names are the property of their respective owners.
V. Third Party Rights
The software may include Third Party Right software. In this case you agree to comply with all
terms and conditions imposed on you in respect of such separate software. In addition to Third
Party Terms, the disclaimer of warranty and limitation of liability provisions in this License shall
apply to the Third Party Right software.
TELIT HEREBY DISCLAIMS ANY AND ALL WARRANTIES EXPRESS OR IMPLIED FROM ANY
THIRD PARTIES REGARDING ANY SEPARATE FILES, ANY THIRD PARTY MATERIALS
INCLUDED IN THE SOFTWARE, ANY THIRD PARTY MATERIALS FROM WHICH THE
SOFTWARE IS DERIVED (COLLECTIVELY “OTHER CODE”), AND THE USE OF ANY OR ALL
THE OTHER CODE IN CONNECTION WITH THE SOFTWARE, INCLUDING (WITHOUT
LIMITATION) ANY WARRANTIES OF SATISFACTORY QUALITY OR FITNESS FOR A
PARTICULAR PURPOSE.
NO THIRD PARTY LICENSORS OF OTHER CODE SHALL HAVE ANY LIABILITY FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING WITHOUT LIMITATION LOST PROFITS), HOWEVER CAUSED AND WHETHER
MADE UNDER CONTRACT, TORT OR OTHER LEGAL THEORY, ARISING IN ANY WAY OUT
OF THE USE OR DISTRIBUTION OF THE OTHER CODE OR THE EXERCISE OF ANY RIGHTS
GRANTED UNDER EITHER OR BOTH THIS LICENSE AND THE LEGAL TERMS APPLICABLE
TO ANY SEPARATE FILES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

JF2 Hardware User Guide Product Applicability
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PRODUCT APPLICABILITY
PRODUCT
JF2
Table 0-1 Product Applicability Table

JF2 Hardware User Guide Contents
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CONTENTS
NOTICES...............................................................................................................................2
COPYRIGHTS .......................................................................................................................2
COMPUTER SOFTWARE COPYRIGHTS.............................................................................2
USAGE AND DISCLOSURE RESTRICTIONS ......................................................................3
PRODUCT APPLICABILITY..................................................................................................4
CONTENTS ...........................................................................................................................5
TABLES.................................................................................................................................8
FIGURES...............................................................................................................................8
INTRODUCTION........................................................................................................9
Purpose .................................................................................................................9
Audience................................................................................................................9
Contact and Support Information............................................................................9
Text Conventions.................................................................................................10
Related Documents..............................................................................................10
1.5.1 Related Documents Requiring a Non-Disclosure Agreement...........................10
PRODUCT VARIANTS.............................................................................................11
FIRMWARE FEATURES AND CONFIGURATION ..................................................12
Low Power Modes................................................................................................12
3.1.1 Full Power .......................................................................................................12
3.1.2 TricklePowerTM ................................................................................................12
3.1.3 Push-To-Fix.....................................................................................................12
3.1.4 Micro Power Mode (MPM)...............................................................................12
Internal LNA.........................................................................................................13
Motion Dynamics..................................................................................................13
3.3.1 Static Navigation..............................................................................................13
3.3.2 Velocity Dead-Reckoning ................................................................................13
3.3.3 MEMS Static Detection....................................................................................13
3.3.4 MEMS Wake-up ..............................................................................................13
MEMS Configuration............................................................................................13
Advanced Features..............................................................................................14
3.5.1 CW Jamming Detection...................................................................................14
3.5.2 SBAS...............................................................................................................14
3.5.3 2-D Acquisition ................................................................................................14
3.5.4 MEMS Compass Heading ...............................................................................14
POWERING THE JF2...............................................................................................15

JF2 Hardware User Guide Contents
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1.8V Supply Voltage.............................................................................................15
4.1.1 EEPROM Powerdown .....................................................................................16
4.1.2 Capacitance ....................................................................................................16
Understanding ON-OFF and SYSTEM-ON ..........................................................17
4.2.1 Auto-ON Configuration (GPIO8 Control)..........................................................17
4.2.2 Powerup Sequence.........................................................................................18
4.2.3 Powerdown Sequence.....................................................................................19
Reset Design Details............................................................................................19
UPDATING THE FIRMWARE: FLASH MODULE (ONLY).......................................20
UPDATING PATCH CODE: EEPROM MODULES AND ROM MODULES WITH HOST
MEMORY.............................................................................................................................21
MAIN SERIAL PORT................................................................................................22
UART Mode.........................................................................................................22
I2C Mode .............................................................................................................23
SPI Mode.............................................................................................................23
Host Message Protocols ......................................................................................24
7.4.1 NMEA Protocol................................................................................................24
7.4.2 OSP Considerations........................................................................................24
MEMS SENSOR/EEPROM INTERFACE .................................................................25
RF FRONT END DESIGN ........................................................................................26
RF Signal Requirements......................................................................................26
GPS Antenna Polarization....................................................................................28
GPS Antenna Gain...............................................................................................28
Active versus Passive Antenna............................................................................29
System Noise Floor..............................................................................................29
External LNA Gain and Noise Figure....................................................................29
Powering an External LNA (active antenna).........................................................30
Implications of the Pre-select SAW Filter..............................................................30
RF Trace Losses..................................................................................................31
RF Interference....................................................................................................31
Shielding..............................................................................................................31
REFERENCE DESIGN.............................................................................................32
RF........................................................................................................................32
Serial Interface (UART)........................................................................................33
Power Control......................................................................................................33
ROM 9600 bps.....................................................................................................33
HANDLING AND SOLDERING................................................................................34
Moisture Sensitivity..............................................................................................34
ESD .....................................................................................................................35

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Reflow..................................................................................................................35
Assembly Issues..................................................................................................35
PCB LAYOUT DETAILS ..........................................................................................36
SAFETY RECOMMENDATIONS..............................................................................37
GLOSSARY AND ACRONYMS...............................................................................38
DOCUMENT HISTORY ............................................................................................42

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TABLES
Table 0-1 Product Applicability Table .......................................................................................... 4
Table 4-1 – Power State Timing..................................................................................................18
Table 7-1 – Operating Interface...................................................................................................22
Table 7-2 – I2C Pin Assignments................................................................................................23
Table 7-3 – SPI Mode Pin Assignments......................................................................................23
FIGURES
Figure 4-1 Initial Application of Power .........................................................................................18
Figure 10-1 JF2 Reference Design – Active Antenna..................................................................32
Figure 11-1 Label for Moisture Sensitive Devices........................................................................34
Figure 12-1 JF2 Pad Design.......................................................................................................36

JF2 Hardware User Guide Introduction
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INTRODUCTION
Purpose
The purpose of this document is to provide information regarding the function, features, and usage
of the Telit products listed in Section Product Applicability
Please refer to that section for details of the members of the product family.
Audience
This document is intended for customer personnel who are responsible for design and
implementation of a GNSS receiver system.
Contact and Support Information
For general contact, technical support services, technical questions, and to report documentation
errors contact Telit Technical Support at:
•[e-mail]
•[e-mail]
•TS-[email protected]
For detailed information about where you can buy the Telit modules or for recommendations on
accessories and components visit:
http://www.telit.com
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.

JF2 Hardware User Guide Introduction
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Text Conventions
All dates are in ISO 8601 format, i.e. YYYY-MM-DD.
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.
Related Documents
Please see the following site for product documentation:
https://www.telit.com/m2m-iot-products/positioning-timing-modules/
JF2 Product Description
JF2 EVK User Guide
1.5.1 Related Documents Requiring a Non-Disclosure Agreement
Telit MT-GNSS Authorized Software User Guide

JF2 Hardware User Guide Product Variants
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PRODUCT VARIANTS
The JF2 module has three variants which have different memory architectures:
Flash – Memory is implemented using flash and is therefore capable of being
reprogrammed to update the firmware image.
ROM – Memory is implemented using read-only and cannot be updated.
EEPROM – ROM memory is augmented by electrically-erasable programmable ROM
which can contain configuration parameters (e.g. baud rate) and patch data.

JF2 Hardware User Guide Firmware Features and Configuration
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FIRMWARE FEATURES AND CONFIGURATION
The JF2 can be configured by means of firmware in order to fit better into the overall system. This
section describes certain aspects of the receiver that can be configured.
Low Power Modes
The JF2 module can be operated in one of four power management modes; Full Power,
TricklePowerTM, Push-To-FixTM, and Micro Power. The latter three of these modes offer
progressively lower power consumption profiles. Depending upon the requirements of the system
design regarding frequency of position updates and availability of GPS signals in the operational
environment, the designer can choose a mode that provides the best trade-off of performance
versus power consumption.
Each of the power management modes can be commanded using the Power Mode Request
Message (MID218), which is available as part of the OSP message set. More details regarding
low power operation can be found in the Low Power Operating Modes Application Note.
3.1.1 Full Power
This mode consumes the most average power, but it is the most accurate navigation mode and
supports the most dynamic motion scenarios.
3.1.2 TricklePowerTM
This mode is a duty-cycling mode. It provides navigation updates at a fixed rate and retains a high
quality of GPS accuracy and dynamic motion response, but at a lower average power cost as
compared to Full Power operation. TricklePower mode produces significant power savings in
strong signal conditions.
3.1.3 Push-To-Fix
This mode provides for even lower power consumption than TricklePower. It is intended for
applications that require infrequent position reports. The position is reported periodically by the
receiver (once every 30 minutes by default) and also when requested. To request a position
update, a pulse is asserted on the ON-OFF pin.
3.1.4 Micro Power Mode (MPM)
Micro Power mode is the lowest power operating mode. Rather than providing position updates at
a reduced rate, it is predicated on maintaining the availability of a navigation solution by maintaining
hot start conditions in the receiver at all times. The receiver is put into Full Power by pulsing the
ON-OFF pin. It is put back into Micro Power mode by sending a Power Mode Request command
to the receiver.

JF2 Hardware User Guide Firmware Features and Configuration
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Internal LNA
The JF2 offers two modes of operation, high gain mode and low gain mode, for the internal LNA.
The high gain mode is the default mode and provides 16 to 20dB of gain. The low gain mode
provides 6 to 10dB of gain.
In general, the high gain mode is intended for use with passive antennas, while the low gain mode
is used when there is an external LNA as part of the RF front end (e.g. active antenna). The
recommended external LNA gain is 20dB.
A version of JF2 firmware is offered for system designs that require the low LNA gain mode. The
gain mode is set by the firmware when the receiver starts up. The Tracker Config message (OSP
MID178, SID2) can also be used to change the LNA mode, but note that the use of this message
is not recommended, because an incorrect parameter could render the JF2 inoperable. Contact
Telit technical support if this approach is required in your system.
Motion Dynamics
3.3.1 Static Navigation
Static navigation, also called position pinning, is a mechanism that it is used by the receiver to
freeze, or pin, the position when the velocity falls below a threshold indicating that the receiver is
stationary. The heading is also frozen, and the velocity is reported as 0. The solution is then
unpinned when the velocity increases above a threshold or when the computed position is a set
distance from the pinned position, indicating that the receiver is in motion again. Note that these
velocity and distance thresholds cannot be changed.
By default, static navigation is disabled. It can be enabled by sending a Static Navigation message
(Message ID 143) with the static navigation flag set to 1. This feature is useful for applications in
which very low dynamics are not expected, the classic example being an automotive application.
3.3.2 Velocity Dead-Reckoning
Velocity dead-reckoning refers to the use of the last known velocity to propagate the navigation
solution when there are insufficient measurements to calculate an updated solution. It serves to
mitigate the effects of blocked satellite signals by continuing to provide a position output. Note that
the receiver outputs status information which indicates whether asolution is being maintainedusing
dead-reckoning.
By default, the receiver operates in dead-reckoning mode for up to 15 seconds before invalidating
the position. This timeout value is considered to be appropriate for most applications. It can be
changed using the Mode Control message (Message ID 136). Valid timeout values are in a range
from zero, which disables dead-reckoning, to two minutes.
3.3.3 MEMS Static Detection
This section is deleted. The sensors are no longer commercially available.
3.3.4 MEMS Wake-up
This section is deleted. The sensors are no longer commercially available.
MEMS Configuration
This section is deleted. The sensors are no longer commercially available.

JF2 Hardware User Guide Firmware Features and Configuration
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Advanced Features
3.5.1 CW Jamming Detection
The JF2 module detects, tracks and removes narrow-band interfering signals (jammers) without
the need for external components or tuning. It monitors a frequency band that is +/- 4MHz from
the L1 frequency for jammers. Any number of jammers that occur outside of a +/-1MHz center
band are removed by the JF2 with a 2MHz band pass filter. Up to eight jammers inside this center
band are removed using a notch filter.
Data regarding detected jammers is output using OSP messages. Message ID 92, Sub ID 1,
reports up to eight of the most recently detected interferers. This feature is useful both in the design
stage and during the production stage for uncovering issues related to unexpected jamming.
3.5.2 SBAS
The JF2 receiver is capable of using Satellite-Based Augmentation System (SBAS) satellites as a
source of both differential corrections and satellite range measurements. These systems (WAAS,
EGNOS, MSAS) use geostationary satellites to transmit regional differential corrections via a GPS-
compatible signal. The use of SBAS corrections can improve typical position accuracy to 3m or
less in open-sky applications.
Note that only an SBAS can be used as source of differential corrections. Other sources such as
data from RTCM beacons are not supported.
By default, the JF2 does not attempt to acquire SBAS satellites. This can be changed by sending
in a DGPS Source command (MID 133) and specifying the source of DGPS corrections as SBAS.
When the receiver acquires SBAS satellites, it will demodulate and use corrections data from the
satellite signal.
The receiver can be configured to compute SBAS satellite range measurements and use them in
the navigation solution. This can be enabled through a control bit in the OSP Mode Control
command (MID 136). See the OSP Manual for details.
3.5.3 2-D Acquisition
By default, the JF2 will compute a 2-D solution when possible when performing initial acquisition.
In a 2-D solution, the receiver assumes a value for altitude and uses it to estimate the horizontal
position. Under warm and hot start conditions, the receiver uses the last known value of altitude,
which is a good assumption in most situations.
However, under cold start conditions the last position is unknown, and the receiver assumes a
value of 0. In situations where the true altitude is significantly higher than that, the horizontal
position estimate will be noticeably impacted. To accommodate applications for which these
situations are a concern, a version of JF2 firmware is offered that requires a calculated altitude, i.e.
a 3-D navigational solution, in order for the receiver to first enter navigation.
3.5.4 MEMS Compass Heading
This section is deleted. The sensors are no longer commercially available.

JF2 Hardware User Guide Powering the JF2
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POWERING THE JF2
1.8V Supply Voltage
Unlike older GPS receiver modules, the JF2 requires a single always on supply voltage of 1.8 volts.
Rather than having a “split” power supply design of main and backup, the JF2 manages all of its
power modes internally.
The 1.8 volt supply must be regulated to be within ±50 mV of nominal voltage inclusive of load
regulation and power supply noise and ripple. Noise and ripple outside of these limits can affect
GPS sensitivity and risk tripping the internal voltage supervisor, thereby shutting down the JF2
unexpectedly. Regulators with very good load regulation are strongly recommended along with
adequate power supply filtering to prevent power supply glitches as the JF2 transitions between
power states.
The power supply voltage, noise and ripple must be between 1.75V and 1.85V for all frequencies
up to 3MHz. Above 3MHz, the noise and ripple component must not exceed ±16 mV. To help meet
these requirements, a separate LDO for the JF2 is suggested.
The JF2 will normally power up into the lowest power “hibernate” state upon initial application of
power. Upon receiving a pulse on the ON-OFF pin, the JF2 will transition to the “operate” state.
Pulsing the ON-OFF signal a second time will transition the JF2 back into the “hibernate” state.
The current power state of the JF2 can be determined by monitoring the “SYSTEM-ON” signal. A
logic low indicates the module is in “hibernate”, whereas logic high indicates the module is in
“operate” state.
If the 1.8 volt DC supply is removed from the JF2 (regardless of power state) it will lose current
RTC time and will lose the contents of the internal SRAM. Serial EEPROM corruption is also
possible if SYSTEM-ON is high. To prevent improper startup, once power is removed, keep the
power removed for approximately 10 seconds so the internal SRAM contents can clear reliably.
The JF2 monitors the 1.8 volt supply and issues an internal hardware reset if the supply drops
below 1.7 volts. This reset protects the flash memory (but not EEPROM) from accidental writes
during a power down condition. Also, the reset clears the RTC time and forces the JF2 into a
hibernate state.

JF2 Hardware User Guide Powering the JF2
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4.1.1 EEPROM Powerdown
This following paragraph applies to the EEPROM variant of the JF2.
The EEPROM write cycles are much longer than power can be maintained internally.
Therefore, it is mandatory to put the module in the HIBERNATE state before removing power to
prevent corruption of the EEPROM. This can be accomplished by the following procedure:
1. Verify that the SYSTEM_ON signal is HIGH indicating that the module is OPERATING.
2. Put the module into the HIBERNATE state by –
a. Sending a pulse to the ON-OFF pin
or
b. Transmitting a HIBERNATE command to the module
3. Monitor the SYSTEM-ON signal and wait for it to go low indicating that the module has
entered the HIBERNATE state.
4. Remove power.
4.1.2 Capacitance
Aluminum electrolytic capacitors are not recommended at the input to the JF2 due to their high
ESR. Tantalum capacitors are recommended with a minimum value of 10uF in parallel with a 0.1uF
ceramic capacitor. Ceramic capacitors are also recommended, but make sure the LDO is stable
with such capacitors tied to the output.

JF2 Hardware User Guide Powering the JF2
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Understanding ON-OFF and SYSTEM-ON
ON-OFF: Input control (pulse)
SYSTEM-ON: Output indicator
The JF2 power is controlled by a state machine. This state machine is clocked by the internal
32 KHz RTC clock, and is controlled by internal signals as well as the ON-OFF and NRESET
signals. The SYSTEM-ON signal reflects the power state of the JF2: logic low for hibernate mode,
and logic high for full power mode.
When power is first applied to the JF2, the internal RTC must start up before the state machine can
begin operating. ON-OFF signals applied before the state machine is ready for them may cause
unpredictable startup. The JF2 signals the readiness to accept ON-OFF signals by outputting a
pulse on the SYSTEM-ON line after power is first applied. This pulse is only output upon application
of power, and is not output when the receiver is in hibernate or full power mode.
The ON-OFF signal must then be pulsed to turn the system ON.
The ON-OFF signal is normally low. When it transitions high, it should stay high for a time equivalent
to a minimum of 3 RTC clock cycles. The signal should then transition low and remain low until the
next change in power state is desired.
If GPIO8 is pulled to logic 1, then the ON-OFF input is modified to be just an ON input.
In this case, it would not be possible to place the JF2 into hibernate by pulsing ON-OFF.
4.2.1 Auto-ON Configuration (GPIO8 Control)
The JF2 powers up directly into the hibernate state (unless GPIO8 is high).
However, it is possible to have the module automatically transition to the full power operating state
by tying the SYSTEM-ON output to the ON-OFF input. GPIO8 should also be tied high, which
changes the ON-OFF signal to just an ON signal. However, this implementation eliminates the
possibility of using the ON-OFF signal to change power states and eliminates the SiRFAware™
and Push-to-Fix™ power modes. If the serial command to place the JF2 in hibernate mode is
issued, the module will transition to the hibernate state with no way other than removal and
reapplication of power (with resulting RTC, SRAM, and EEPROM data loss) to force the module to
power up. For some users, this may be all that is required if time and data retention are not
important during a power down situation. The user is still required to monitor SYSTEM-ON and
maintain power until it goes low.
GPIO8 is used differently on the SE868-V2 (LNA Gain control) and the SE868-V3 (LNA-ENABLE).
ON-OFF is also different on the SE868-V3 where it is level-sensitive..

JF2 Hardware User Guide Powering the JF2
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4.2.2 Powerup Sequence
Powerup Sequence (with GPIO8 low) –
1. The ON-OFF input must be low.
2. Apply power.
3. Wait for the short pulse from SYSTEM-ON
4. Send a pulse to the ON-OFF pin. Note: see 4.2.1Auto-ON Configuration (GPIO8 Control)for
alternative method.
5. The module will begin operation and is now ready to accept input commands.
VDD 18
ON-OFF
SYSTEM-ON
(clock runs)
Unknown
Unknown
∆T1
∆T2
∆THIGH
RTC CLK
(INTERNAL)
Figure 4-1 Initial Application of Power
Timed Parameter Prior Event/State Symbol Min Typ Max Unit
RTC startup time First power
applied T10 299 5000 ms
FSM Ready pulse RTC running T210 TRTC
Min ON-OFF high THIGH 3 TRTC
TRTC is equivalent to one RTC (32.678KHz) clock cycle.
Table 4-1 – Power State Timing

JF2 Hardware User Guide Powering the JF2
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4.2.3 Powerdown Sequence
Powerdown Sequence
1. The ON-OFF input must be low.
2. Verify that SYSTEM-ON is high.
3. Put the module into the HIBERNATE state -
a. Send a pulse to the ON-OFF pin. (assuming GPIO8 low)
OR
b. Issue a hibernate command ($PSRF117 or OSP MID 205)
4. Wait for the SYSTEM-ON signal to go low.
5. Remove power.
Reset Design Details
The JF2 NRESET pin is normally connected to a 0.33uF ceramic capacitor. The JF2 will generate
an internal reset as appropriate. No external reset signal needs to be applied to the JF2.
If an external reset is desired, the signal must be either open collector or open drain without any
form of pullup. Do not pull this line high with either a pullup or a driven logic one.
When this line is pulled low, the JF2 will immediately drop into hibernate mode with some loss of
data.
Whenthe external reset is released,the JF2 will go through its normal power up sequence provided
the VCC_IN supply is within specifications. Note that a “ready” pulse on SYSTEM-ON will not be
issued.

JF2 Hardware User Guide Updating the Firmware: Flash Module (ONLY)
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UPDATING THE FIRMWARE: FLASH MODULE (ONLY)
During normal operations, the BOOT signal should be tied to ground through a 100K pulldown
resistor. This will ensure the GPS module executes the code out of the internal flash memory.
However, if the internal flash memory needs to be updated, the following steps should be performed
to place the JF2 module into a state suitable for programming the internal flash memory.
1. Either remove all power to the module, or force the module into hibernate state
by pulsing the ON-OFF signal. Verify the state of the module by monitoring the
SYSTEM-ON signal is low.
2. Pull the BOOT signal high through a 10K pull up resistor to +1.8 volts.
3. Apply main power if not already applied.
4. Pulse the ON-OFF signal to place the JF2 module into BOOT mode.
5. Run the software utility to re-flash the JF2 module. Clearing the entire flash
memory is strongly recommended prior to programming.
6. Upon successful completion of re-flashing, remove main power to the module
for a minimum of 10 seconds.
7. Pull the BOOT signal low through a 100K pull down resistor to GND.
8. Apply main power to the JF2.
9. Pulse the ON-OFF signal to place the JF2 into the normal operating state.