Specifications

Chapter 3 – Electrical Characteristics
Wireless ModemModule GSM/GPRS Developer’s Guide 19
Serial Link
A serial link interface is available complying with V24 protocol signaling but not with V28 (electrical interface) due
to a 2.8 Volts interface. TX, RTS and DTR can be either 5V or 3V. Data signals are Hi = Mark. Controls signals
are Hi = Off.
The signals are Tx data (CT103/TX), Rx data (CT104/RX), Request To Send (CT105/RTS), Clear To Send
(CT106/CTS), Data Terminal Ready (CT108-2/DTR), Data Carrier Detect (CT109/DCD), Ring Indicator
(CT125/RI), and Data Set Ready (CT107/DSR).
Table 3-8: Serial Link Pin Description
Signal Pin Number I/O I/O Type* Description
CT103 / TX 25 I CMOS Transmit serial data
CT104 / RX 28 O 1X Receive serial data
CT105 / RTS 30 I CMOS Ready to send
CT106 / CTS 13 O 1X Clear to send
CT107 / DSR 27 O 1X Data set ready
CT108-2 / DTR 29 I CMOS Data terminal ready
CT109 / DCD 5 O CMOS / 2X Data carrier detect
CT125 / RI 9 O CMOS / 2X Ring indicator
* See “Table 3-2: Operating Conditions” in section on the 50-pin Connector Description.