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GM47/GM48 INTEGRATOR’S MANUAL
56
LZT 123 7263 R1C
Note! UART1 signal levels do not match standard RS232 (V.28) levels. The
relationship between the levels is shown in the table below.
Conversion between the module CMOS levels and RS232 levels can be
achieved using a standard interface IC, such as the Maxim Integrated
Products MAX3237.
2.8.2 Serial Data Signals - RD, TD
The default baud rate is 9.6kbits/s, however higher bit rates of up to
460 kbits/s are supported, set by an AT command. UART1 starts at a
rate of 9.6kbits/s in standard AT command mode. The module also
supports GSM 07.10 multiplexing protocol and starts when the
appropriate command is sent.
Serial Data From Module (RD)
RD is an output signal that the module uses to send data via UART1 to
the application.
Serial Data To Module (TD)
TD is an input signal, used by the application to send data via UART1
to the module.
2.8.3 Control Signals - RTS, CTS, DTR, DCD, RI
UART1 control signals are active low and need a standard interface IC,
such as the MAX3237, to generate standard RS232 levels.
UART1 converted signals, together with DGND, RD and TD form a
9-pin RS232 data port.
RS232 level RD, TD RTS, CTS, DTR, DCD, RI CMOS level
<–3V 1 OFF >1.93V
>+3V 0 ON <0.80V
Parameter Limit
Application load resistance ≥100kΩ
Application load capacitance <100pF
Parameter Limit
Application driving impedance <100Ω
Input capacitance <100pF
Input resistance <100Ω in series, with 100kΩ to DGND