User Manual

GM47/48 Technical description

BA/SEM/MS 02:0004 Rev B

3.10.1 UART 1 (RS232) - RD, TD, RTS, CTS, DTR, DCD and RI

The UART1 signals form a 9 pin RS-232 (V.24) serial port, apart

from the DSR (CCITT Nº 107) signal. DSR signal has been removed

as it is usually connected to DTR in most systems.

The signal levels do not match the standard RS-232 (V.28) levels. The

relationship between the levels is shown in the table below

RS - 232 Level RD, TD RTS, CTS, DTR, DCD, RI 2.75 V CMOS Level

< - 3 V 1 OFF > 1.93

> + 3 V 0 ON < 0.80 V

Conversion between the 2.75V CMOS levels and the RS232 levels

can be achieved using a standard interface IC, such as the Maxim

Integrated Products MAX3237.

3.10.2 Serial Data Signals - RD, TD

The default baud rate is 9.6 kbit/s, however higher bit rates up to 460

kbit/s shall be supported, and set by an AT command. The UART 1

starts at a rate of 9.6 kbit/s in standard AT mode or binary mode (First

received data AT or binary will determine the operation mode).

The GSM 07.10 multiplexing protocol is supported and shall be

started on command. In this case bit rates up to 460 kbits/s shall be

supported.

Serial Data From Module (RD)

RD is an output used to send data on the UART 1 to the application

system. This is a Dig. 2.75 CMOS Output and general characteristics

are applicable.

Parameter Limit

Application load resistance

< 100 kΩ

Application load capacitance < 500 pF

Serial Data To Module (TD)

TD is input (to the module) used by the application system to send

data on the UART 1 to the module. This is a Dig. 2.75 CMOS Input

and general characteristics are applicable.

Parameter Limit

Application driving impedance

< 100 Ω

Input capacitance 1 nF

Input resistance (pull-up)

100 kΩ to 2.75 V