DS-GSMT35I-2

Oct ’07

www.rfsolutions.co.uk

©

2007 REG No 277 4001, ENGLAND.

Page 4

2

Interface description

The TMAS GSM Terminal provides the following connectors for power supply, interfacing and antenna:

•

2.1mm DC power connector (centre/inner pin is positive)

•

9-pin (female) D-SUB plug for RS-232 serial interface

•

SMA connector for antenna (radio interface)

•

SIM card holder

2.1 Power Supply

The power supply of the TMAS GSM Terminal has to be a single voltage source of Vin=6V providing a peak

current of up to 500mA during transmission.

The terminal can be turned on by just plug in a 6VDC power supply. The terminal power supply circuit

automatically generates a low pulse signal not less than 100ms in order to wake up the Siemens TC35i GSM

engine.

In order for the terminal to shut down properly, wait for 10s after sending AT^SMSO before switching off the

power supply. This time is needed for the module to be safely logged off from the network and finish saving

data to the internal memory.

Each time the terminal is shut down, data will be written from the volatile memory to flash memory. The

guaranteed maximum number of write cycles is limited to 100,000.

2.2 RS232 Interface

Via RS-232 interface, the host controller controls the TMAS GSM/GPRS Terminal and transports data. The

table below shows the pin assignment of RS-232 (D-SUB 9-pin female).

TMAS GSM/GPRS Terminal is designed for use as DCE. Based on the conventions for DCE-DTE connection,

it communicates with the user application (DTE) using the following signals:

Pin no.

Signal name

I/O

Function

1

/DCD

O

Data Carrier Detected

2

/RXD

O

Receive Data

3

/TXD

I

Transmit Data

4

/DTR

I

Data Terminal Ready

5

GND

-

Ground

6

/DSR

O

Data Set Ready

7

/RTS

I

Request To Send

8

/CTS

O

Clear To Send

9

/RI

O

Ring Indication