Telit Communications S p A GE863 Users Manual

Telit GE863-QUAD / GE863-PY

Hardware User guide

1vv0300697, Rev. ISSUE#0, - 21/11/05

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Telit GE863-QUAD / GE863-PY

Hardware User guide

1vv0300697, Rev. ISSUE#0, - 21/11/05

Contents

1 OVERVIEW 5

2 HARDWARE COMMANDS 6

2.1 Turning ON the GE863-QUAD 6

2.2 Turning OFF the GE863-QUAD 8

2.2.1 Hardware shutdown 8

2.3 Hardware Unconditional Reboot 8

3 POWER SUPPLY 10

3.1 Power Supply Requirements 10

3.2 General Design Rules 10

3.2.1 Electrical design Guidelines 11

3.2.1.1 + 5V input Source Power Supply Design Guidelines 11

3.2.1.2 + 12V input Source Power Supply Design Guidelines 12

3.2.1.3 Battery Source Power Supply Design Guidelines 13

3.2.1.4 Battery Charge control Circuitry Design Guidelines 13

3.2.2 Thermal Design Guidelines 15

3.2.3 Power Supply PCB layout Guidelines 16

4 ANTENNA 17

4.1 Antenna Requirements 17

4.2 Antenna PCB line Guidelines 18

4.3 Antenna installation Guidelines 19

5 SERIAL PORT 20

5.1 RS232 level translation 22

5.2 5V UART level translation 24

6 MICROPHONE 26

6.1 Microphone line Characteristic and requirements 26

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6.2 General Design Rules 29

6.3 Microphone Biasing 29

6.3.1 Balanced Microphone biasing 30

6.3.2 Unbalanced Microphone biasing 31

6.4 Microphone buffering 32

6.4.1 Buffered Balanced Mic. 32

6.4.2 Buffered Unbalanced (Single Ended) Mic. 34

7 SPEAKER 37

7.1 Speaker lines characteristics and requirements 37

7.2 General Design rules 39

7.2.1 Noise Filtering 40

7.3 Handset earphone design 40

7.4 Hands Free earphone (low power) design 42

7.5 Car Kit speakerphone design 42

8 GENERAL PURPOSE I/O 44

8.1 Using a GPIO pad as INPUT 44

8.2 Using a GPIO pad as OUTPUT 44

8.3 Using the Alarm Output GPIO6 45

8.4 Using the Buzzer Output GPIO7 45

9 CAMERA 46

9.1 Agilent Camera 46

9.1.1 Camera interface connectors 46

9.2 Transchip Camera 48

9.2.1 Camera interface connectors 48

9.2.2 EVB for Agilent and Transchip camera support 51

9.2.3 Block Diagram for supported cameras 52

9.2.4 Schematic Diagrams for supported cameras 53

9.2.5 Example usage script for camera 55

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Hardware User guide

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DOCUMENT CHANGE LOG 57

10 ANNEX A - EVK SCHEMATICS 58

Telit GE863-QUAD / GE863-PY

Hardware User guide

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1 Overview

The aim of this document is the description of some hardware solutions useful for developing a

product with the Telit GE863-QUAD module.

In this document all the basic functions of a mobile phone will be taken into account; for each one of them a proper hardware solution will be suggested and eventually the wrong solutions and common errors to be avoided will be evidenced. Obviously this document can not embrace the whole hardware solutions and products that may be designed. The wrong solutions to be avoided shall be considered as mandatory, while the suggested hardware configurations shall not be considered mandatory, instead the information given shall be used as a guide and a starting point

for properly developing your product with the Telit GE863-QUAD module. For further hardware

details that may not be explained in this document refer to the Telit GE863-QUAD Product Description document where all the hardware information is reported.

NOTICE

The information presented in this document is believed to be accurate and reliable. However, no responsibility is assumed by Telit Communication S.p.A. for its use, nor any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent rights of Telit Communication S.p.A. other than for circuitry embodied in Telit products. This document is subject to change

without notice

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Hardware User guide

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2 Hardware Commands

2.1 Turning ON the GE863-QUAD

To turn on the GE863-QUAD the pad ON# must be tied low for at least 1 second and then released.

The maximum current that can be drained from the ON# pad is 0,1 mA.

A simple circuit to do it is:

ON#

Power ON impulse

GND

NOTE: don't use any pull up resistor on the ON# line, it is internally pulled up. Using pull up resistor may bring to latch up problems on the GE863-QUAD power regulator and improper power on/off of the module. The line ON# must be connected only in open collector configuration.

NOTE: In this document all the lines that are inverted, hence have active low signals are labeled with a name that ends with a "#" or with a bar over the name.

NOTE: The GE863-QUAD turns fully on also by supplying power to the Charge pad (provided there's a battery on the VBATT pads).

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For example:

1- Let's assume you need to drive the ON# pad with a totem pole output of a +3/5 V microcontroller (uP_OUT1):

2- Let's assume you need to drive the ON# pad directly with an ON/OFF button:

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2.2 Turning OFF the GE863-QUAD

The turning off of the device can be done in three ways:

• by software command (see GE863-QUAD Software User Guide)

• by hardware shutdown

When the device is shut down by software command or by hardware shutdown, it issues to the network a detach request that informs the network that the device will not be reachable any more.

2.2.1 Hardware shutdown

To turn OFF the GE863-QUAD the pad ON# must be tied low for at least 1 second and then released.

The same circuitry and timing for the power on shall be used.

The device shuts down after the release of the ON# pad.

TIP: To check if the device has powered off, the hardware line PWRCTL should be monitored. When PWRCTL goes low, the device has powered off.

2.3 Hardware Unconditional Reboot

To unconditionally Reboot the GE863-QUAD, the pad RESET# must be tied low for at least 200 milliseconds and then released.

The maximum current that can be drained from the ON# pad is 0,15 mA.

A simple circuit to do it is:

Unconditional Reboot impulse

RESET#

GND

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NOTE: don't use any pull up resistor on the RESET# line nor any totem pole digital output. Using pull up resistor may bring to latch up problems on the GE863-QUAD power regulator and improper functioning of the module. The line RESET# must be connected only in open collector configuration.

TIP: The unconditional hardware reboot should be always implemented on the boards and software should use it as an emergency exit procedure.

For example:

1- Let's assume you need to drive the RESET# pad with a totem pole output of a +3/5 V microcontroller (uP_OUT2):

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3 Power Supply

The power supply circuitry and board layout are a very important part in the full product design and they strongly reflect on the product overall performances, hence read carefully the requirements and the guidelines that will follow for a proper design.

3.1 Power Supply Requirements

The GE863-QUAD power requirements are:

• Nominal Supply Voltage: 3.8 V

• Max Supply Voltage: 4.2 V

• Supply voltage range: 3.4 V - 4.2 V

• Max Peak current consumption (impulsive): 1.9 A

• Max Average current consumption during GPRS transmission (rms): 500 mA

• Max Average current consumption during VOICE/CSD transmission (rms): 270 mA

• Average current during Power Saving: ≈ 4 mA

• Average current during idle (Power Saving disabled) ≈ 19 mA

The GSM system is made in a way that the RF transmission is not continuous, else it is packed into bursts at a base frequency of about 216 Hz, the relative current peaks can be as high as about 2A. Therefore the power supply has to be designed in order to withstand with these current peaks without big voltage drops; this means that both the electrical design and the board layout must be designed for this current flow.

If the layout of the PCB is not well designed a strong noise floor is generated on the ground and the supply; this will reflect on all the audio paths producing an audible annoying noise at 216 Hz; if the voltage drop during the peak current absorption is too much, then the device may even shutdown as a consequence of the supply voltage drop.

TIP: The electrical design for the Power supply should be made ensuring it will be capable of a peak current output of at least 2 A.

3.2 General Design Rules

The principal guidelines for the Power Supply Design embrace three different design steps:

- the electrical design

- the thermal design.

- the PCB layout.

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3.2.1 Electrical design Guidelines

The electrical design of the power supply depends strongly from the power source where this power is drained. We will distinguish them into three categories:

• +5V input (typically PC internal regulator output)

• +12V input (typically automotive)

• Battery

3.2.1.1 + 5V input Source Power Supply Design Guidelines

• The desired output for the power supply is 3.8V, hence there's not a big difference between the input source and the desired output and a linear regulator can be used. A switching power supply will not be suited because of the low drop out requirements.

• When using a linear regulator, a proper heat sink shall be provided in order to dissipate the power generated.

• A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the current absorption peaks close to the GE863-QUAD, a 100μF tantalum capacitor is usually suited.

• Make sure the low ESR capacitor on the power supply output (usually a tantalum one) is rated at least 10V.

• A protection diode should be inserted close to the power input, in order to save the GE863QUAD from power polarity inversion.

An example of linear regulator with 5V input is:

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3.2.1.2 + 12V input Source Power Supply Design Guidelines

• The desired output for the power supply is 3.8V, hence due to the big difference between the input source and the desired output, a linear regulator is not suited and shall not be used. A switching power supply will be preferable because of its better efficiency especially with the 2A peak current load represented by the GE863-QUAD.

• When using a switching regulator, a 500kHz or more switching frequency regulator is preferable because of its smaller inductor size and its faster transient response. This allows the regulator to respond quickly to the current peaks absorption.

• For car PB battery the input voltage can rise up to 15,8V and this should be kept in mind when choosing components: all components in the power supply must withstand this voltage.

• A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the current absorption peaks, a 100μF tantalum capacitor is usually suited.

• Make sure the low ESR capacitor on the power supply output (usually a tantalum one) is rated at least 10V.

• For Car applications a spike protection diode should be inserted close to the power input, in order to clean the supply from spikes.

• A protection diode should be inserted close to the power input, in order to save the GE863QUAD from power polarity inversion. This can be the same diode as for spike protection.

An example of switching regulator with 12V input is:

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3.2.1.3 Battery Source Power Supply Design Guidelines

• The desired nominal output for the power supply is 3.8V and the maximum voltage allowed is 4.2V, hence a single 3.7V Li-Ion cell battery type is suited for supplying the power to the Telit GE863-QUAD module.

The three cells Ni/Cd or Ni/MH 3,6 V Nom. battery types or 4V PB types MUST NOT BE USED DIRECTLY since their maximum voltage can rise over the absolute maximum

voltage for the GE863-QUAD and damage it.

NOTE: DON'T USE any Ni-Cd, Ni-MH, and Pb battery types directly connected with GE863-QUAD. Their use can lead to overvoltage on the GE863-QUAD and damage it. USE ONLY Li-Ion battery types.

• A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the current absorption peaks, a 100μF tantalum capacitor is usually suited.

• Make sure the low ESR capacitor (usually a tantalum one) is rated at least 10V.

• A protection diode should be inserted close to the power input, in order to save the GE863-

QUAD from power polarity inversion. Otherwise the battery connector should be done in a way to avoid polarity inversions when connecting the battery.

• The battery capacity must be at least 500mAh in order to withstand the current peaks of 2A; the suggested capacity is from 500mAh to 1000mAh.

3.2.1.4 Battery Charge control Circuitry Design Guidelines

The charging process for Li-Ion Batteries can be divided into 4 phases:

• Qualification and trickle charging

• Fast charge 1 - constant current

• Final charge - constant voltage or pulsed charging

• Maintenance charge

The qualification process consists in a battery voltage measure, indicating roughly its charge status. If the battery is deeply discharged, that means its voltage is lower than the trickle charging threshold, then the charge must start slowly possibly with a current limited precharging process where the current is kept very low with respect to the fast charge value: the trickle charging.

During the trickle charging the voltage across the battery terminals rises; when it reaches the fast charge threshold level the charging process goes into fast charge phase.

During the fast charge phase the process proceeds with a current limited charging; this current limit depends on the required time for the complete charge and from the battery pack capacity. During this phase the voltage across the battery terminals still raises but at a lower rate.

Once the battery voltage reaches its maximum voltage then the process goes into its third state: Final charging. The voltage measure to change the process status into final charge is very

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important. It must be ensured that the maximum battery voltage is never exceeded, otherwise the battery may be damaged and even explode. Moreover for the constant voltage final chargers, the constant voltage phase (final charge) must not start before the battery voltage has reached its maximum value, otherwise the battery capacity will be highly reduced.

The final charge can be of two different types: constant voltage or pulsed. GE863-QUAD uses constant voltage.

The constant voltage charge proceeds with a fixed voltage regulator (very accurately set to the maximum battery voltage) and hence the current will decrease while the battery is becoming charged. When the charging current falls below a certain fraction of the fast charge current value, then the battery is considered fully charged, the final charge stops and eventually starts the maintenance.

The pulsed charge process has no voltage regulation, instead the charge continues with pulses. Usually the pulse charge works in the following manner: the charge is stopped for some time, let's say few hundreds of ms, then the battery voltage will be measured and when it drops below its maximum value a fixed time length charging pulse is issued. As the battery approaches its full charge the off time will become longer, hence the duty-cycle of the pulses will decrease. The battery is considered fully charged when the pulse duty-cycle is less than a threshold value, typically 10%, the pulse charge stops and eventually the maintenance starts.

The last phase is not properly a charging phase, since the battery at this point is fully charged and the process may stop after the final charge. The maintenance charge provides an additional charging process to compensate for the charge leak typical of a Li-Ion battery. It is done by issuing pulses with a fixed time length, again few hundreds of ms, and a duty-cycle around 5% or less.

This last phase is not implemented in the GE863-QUAD internal charging algorithm, so that the battery once charged is left discharging down to a certain threshold so that it is cycled from full charge to slight discharge even if the battery charger is always inserted. This guarantees that anyway the remaining charge in the battery is a good percentage and that the battery is not damaged by keeping it always fully charged (Li-Ion rechargeable battery usually deteriorate when kept fully charged).

Last but not least, in some applications it is highly desired that the charging process restarts when the battery is discharged and its voltage drops below a certain threshold, GE863-QUAD internal charger does it.

As you can see, the charging process is not a trivial task to be done; moreover all these operations should start only if battery temperature is inside a charging range, usually 5°C - 45°C.

The GE863-QUAD measures the temperature of its internal component, in order to satisfy this last requirement, it's not exactly the same as the battery temperature but in common application the two temperature should not differ too much and the charging temperature range should be guaranteed.

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NOTE: For all the threshold voltages, inside the GE863-QUAD all threshold are fixed in order to maximize Li-Ion battery performances and do not need to be changed.

NOTE: In this application the battery charger input current must be limited to less than 400mA. This can be done by using a current limited wall adapter as the power source.

3.2.2Thermal Design Guidelines

The thermal design for the power supply heat sink should be done with the following specifications:

• Average current consumption during transmission @PWR level max (rms): 500mA

• Average current consumption during transmission @ PWR level min (rms): 100mA

• Average current during Power Saving: 4mA

• Average current during idle (Power Saving disabled) 19mA

NOTE: The average consumption during transmissions depends on the power level at which the device is requested to transmit by the network. The average current consumption hence varies significantly.

TIP: The thermal design for the Power supply should be made keeping a average consumption at the max transmitting level during calls of 500mA rms.

Considering the very low current during idle, especially if Power Saving function is enabled, it is possible to consider from the thermal point of view that the device absorbs current significantly only during calls.

If we assume that the device stays into transmission for short periods of time (let's say few minutes) and then remains for a quite long time in idle (let's say one hour), then the power supply has always the time to cool down between the calls and the heat sink could be smaller than the calculated one for 500mA maximum RMS current, or even could be the simple chip package (no heat sink).

Moreover in the average network conditions the device is requested to transmit at a lower power level than the maximum and hence the current consumption will be less than the 500mA, being usually around 150mA.

For these reasons the thermal design is rarely a concern and the simple ground plane where the power supply chip is placed can be enough to ensure a good thermal condition and avoid overheating.

For the heat generated by the GE863-QUAD, you can consider it to be during transmission 1W max during CSD/VOICE calls and 2W max during class10 GPRS upload.

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This generated heat will be mostly conducted to the ground plane under the GE863-QUAD, you must ensure that your application can dissipate it.

3.2.3 Power Supply PCB layout Guidelines

As seen on the electrical design guidelines the power supply shall have a low ESR capacitor on the output to cut the current peaks and a protection diode on the input to protect the supply from spikes and polarity inversion. The placement of these components is crucial for the correct working of the circuitry. A misplaced component can be useless or can even decrease the power supply performances.

• The Bypass low ESR capacitor must be placed close to the Telit GE863-QUAD power input pads or in the case the power supply is a switching type it can be placed close to the inductor to cut the ripple provided the PCB trace from the capacitor to the GE863-QUAD is wide enough to ensure a dropless connection even during the 2A current peaks.

• The protection diode must be placed close to the input connector where the power source is drained.

• The PCB traces from the input connector to the power regulator IC must be wide enough to ensure no voltage drops occur when the 2A current peaks are absorbed. Note that this is not made in order to save power loss but especially to avoid the voltage drops on the power line at the current peaks frequency of 216 Hz that will reflect on all the components connected to that supply, introducing the noise floor at the burst base frequency. For this reason while a voltage drop of 300-400 mV may be acceptable from the power loss point of view, the same voltage drop may not be acceptable from the noise point of view. If your application doesn't have audio interface but only uses the data feature of the Telit GE863-QUAD, then this noise is not so disturbing and power supply layout design can be more forgiving.

• The PCB traces to the GE863-QUAD and the Bypass capacitor must be wide enough to ensure no significant voltage drops occur when the 2A current peaks are absorbed. This is for the same reason as previous point. Try to keep this trace as short as possible.

• The PCB traces connecting the Switching output to the inductor and the switching diode must be kept as short as possible by placing the inductor and the diode very close to the power switching IC (only for switching power supply). This is done in order to reduce the radiated field (noise) at the switching frequency (100-500 kHz usually).

• The use of a good common ground plane is suggested.

• The placement of the power supply on the board should be done in such a way to guarantee

that the high current return paths in the ground plane are not overlapped to any noise sensitive circuitry as the microphone amplifier/buffer or earphone amplifier.

• The power supply input cables should be kept separate from noise sensitive lines such as microphone/earphone cables.

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4 Antenna

The antenna connection and board layout design are the most important part in the full product design and they strongly reflect on the product overall performances, hence read carefully and follow the requirements and the guidelines for a proper design.

4.1 Antenna Requirements

As suggested on the Product Description the antenna and antenna line on PCB for a Telit GE863-QUAD device shall fulfil the following requirements:

ANTENNA REQUIREMENTS

Frequency range

Bandwidth

Gain

Impedance

Input power

VSWR absolute max

VSWR recommended

When using the Telit GE863-QUAD, since there's no antenna connector on the module, the antenna must be connected to the GE863-QUAD through the PCB with the antenna pad.

Standard Dual Band GSM/DCS frequency range or

Standard Quad Band GSM/DCS/PCS frequency range if used for all four bands

80 MHz in GSM & 170 MHz in DCS & 140 MHz PCS band

Gain < 3dBi

50 ohm

> 2 W peak power

<= 10:1

<= 2:1

In the case that the antenna is not directly developed on the same PCB, hence directly connected at the antenna pad of the GE863-QUAD, then a PCB line is needed in order to connect with it or with its connector.

Telit GE863-QUAD / GE863-PY

This line of transmission shall fulfil the following requirements:

ANTENNA LINE ON PCB REQUIREMENTS

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Impedance

Max Attenuation

No coupling with other signals allowed

Cold End (Ground Plane) of antenna shall be equipotential to the GE863-QUAD ground pins

Furthermore if the device is developed for the US market and/or Canada market, it shall comply to the FCC and/or IC approval requirements:

This device is to be used only for mobile and fixed application. The antenna(s) used for this transmitter must be installed to provide a separation distance of at least 20 cm from all persons and must not be co-located or operating in conjunction with any other antenna or transmitter. End-Users must be provided with transmitter operation conditions for satisfying RF exposure compliance. OEM integrators must ensure that the end user has no manual instructions to remove or install the GE863-QUAD module. Antennas used for this OEM module must not exceed 3dBi gain for mobile and fixed operating configurations.

50 ohm

0,3 dB

4.2 Antenna PCB line Guidelines

• Ensure that the antenna line impedance is 50 ohm;

• Keep the antenna line on the PCB as short as possible, since the antenna line loss shall be

less than 0,3 dB;

• Antenna line must have uniform characteristics, constant cross section, avoid meanders and abrupt curves;

• Keep, if possible, one layer of the PCB used only for the Ground plane;

• Surround (on the sides, over and under) the antenna line on PCB with Ground, avoid having

other signal tracks facing directly the antenna line track;

• The ground around the antenna line on PCB has to be strictly connected to the Ground Plane by placing vias once per 2mm at least;

• Place EM noisy devices as far as possible from GE863-QUAD antenna line;

• Keep the antenna line far away from the GE863-QUAD power supply lines;

• If you have EM noisy devices around the PCB hosting the GE863-QUAD, such as fast

switching ICs, take care of the shielding of the antenna line by burying it inside the layers of PCB and surround it with Ground planes, or shield it with a metal frame cover.

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• If you don't have EM noisy devices around the PCB of GE863-QUAD, by using a strip-line on the superficial copper layer for the antenna line, the line attenuation will be lower than a buried one;

4.3 Antenna installation Guidelines

• Install the antenna in a place covered by the GSM signal.

• The Antenna must be installed to provide a separation distance of at least 20 cm from all

persons and must not be co-located or operating in conjunction with any other antenna or transmitter;

• Antenna shall not be installed inside metal cases

• Antenna shall be installed also according Antenna manufacturer instructions.

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5 Serial Port

The serial port on the Telit GE863-QUAD is the core of the interface between the module and OEM hardware. Several configurations can be designed for the serial port on the OEM hardware, but the most common are:

- RS232 PC com port

- microcontroller UART @ 2.8V - 3V (Universal Asynchronous Receive Transmit)

- microcontroller UART@ 5V or other voltages different from 2.8V

Depending from the type of serial port on the OEM hardware a level translator circuit may be needed to make the system work. The only configuration that doesn't need a level translation is the 2.8V UART.

The serial port on the GE863-QUAD is a +2.8V UART with all the 7 RS232 signals. It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels. The levels for the GE863-QUAD UART are the CMOS levels:

Absolute Maximum Ratings -Not Functional

Parameter Min Max

Input level on any digital pad when on

Input voltage on analog pads when on

Operating Range - Interface levels (2.8V CMOS)

Level Min Max

Input high level V

Input low level VIL 0V 0.5V

Output high level VOH2.2V 3.0V

-0.3V +3.75V

-0.3V +3.0 V

2.1V 3.3V

Output low level VOL0V 0.35V

The signals of the GE863-QUAD serial port are:

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RS232

Number

1 DCD -

2 RXD -

3 TXD -

4 DTR -

5 GND 8-17-28-36-

6 DSR -

7 RTS -

8 CTS -

Signal GE863-

QUAD Pad

Number

dcd_uart

tx_uart

rx_uart

dtr_uart

45-48-50-56

dsr_uart

rts_uart

cts_uart

Name Usage

42 Data Carrier Detect Output from the GE863-QUAD that

indicates the carrier presence

38 Transmit line *see Note Output transmit line of GE863-QUAD

UART

37 Receive line *see Note Input receive of the GE863-QUAD UART

39 Data Terminal Ready Input to the GE863-QUAD that controls

the DTE READY condition

Ground ground

43 Data Set Ready Output from the GE863-QUAD that

indicates the module is ready

40 Request to Send Input to the GE863-QUAD that controls

the Hardware flow control

41 Clear to Send Output from the GE863-QUAD that

controls the Hardware flow control

9 RI -

ri_uart

NOTE: According to V.24, RX/TX signal names are referred to the application side, therefore on the GE863-QUAD side these signal are on the opposite direction: TXD on the application side will be connected to the receive line (here named TXD/ rx_uart ) of the GE863-QUAD serial port and viceversa for RX.

TIP: For a minimum implementation, only the TXD and RXD lines can be connected, the other lines can be left open provided a software flow control is implemented.

The signals in the UART connector on the EVK are:

44 Ring Indicator Output from the GE863-QUAD that

indicates the incoming call condition

DCD RXD

TXD DTR

GND DSR

RTS CTS

RI GND

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