Integrator's Manual GR47/GR48

5. SYSTEM CONNECTOR INTERFACE
37
LZT 123 7589 R1A
Digital 2.75 V CMOS input/output electrical characteristics apply.
The standard character format consists of 1 start bit, 8 bit data, no parity
and 1 stop bit. In all, there are 10 bits per character.
5.9.1 UART1 (RS232) - RD, TD, RTS, CTS, DTR, DSR, DCD and RI
UART1 signals conform to a 9-pin RS232 (V.24) serial port.
1RWH 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 radio device CMOS levels and RS232 levels can be
achieved using a standard interface IC, such as the Maxim Integrated
Products MAX3237.
5.9.2 Serial Data Signals - RD, TD
The default baud rate is 9.6 kbits/s, however higher bit rates of up to
460 kbits/s are supported, set by an AT command. UART1 starts at a rate
of 9.6 kbits/s in standard AT command mode. The radio device also
supports GSM 07.10 multiplexing protocol and starts when the
appropriate command is sent.
Serial Data From Radio Device (RD)
RD is an output signal that the radio device uses to send data via UART1
to the application.
Serial Data To Radio Device (TD)
TD is an input signal, used by the application to send data via UART1 to
the radio device.
RS232 level RD, TD RTS, CTS, DTR, DSR, DCD, RI CMOS level
< – 3 V 1 OFF > 1.93 V
> + 3 V 0 ON < 0.80 V
Parameter Limit
Application load resistance < 100 kΩ
Application load capacitance < 100 pF
Parameter Limit
Application driving impedance < 100 Ω
Input capacitance 1nF
Input resistance 100 kΩ to 2.75 V