Table of Contents
Advertisement
5.9.1 UART1 (RS232) - RD, TD, RTS, CTS, DTR, DSR, DCD and RI
5.9.2 Serial Data Signals - RD, TD
Serial Data From Radio Device (RD)
Serial Data To Radio Device (TD)
LZT 123 7589 R1A
5. SYSTEM CONNECTOR INTERFACE
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.
UART1 signals conform to a 9-pin RS232 (V.24) serial port.
UART1 signal levels do not match standard RS232 (V.28) levels. The
relationship between the levels is shown in the table below.
RS232 level
RD, TD
< – 3 V
1
> + 3 V
0
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.
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.
RD is an output signal that the radio device uses to send data via UART1
to the application.
Parameter
Application load resistance
Application load capacitance
TD is an input signal, used by the application to send data via UART1 to
the radio device.
Parameter
Application driving impedance
Input capacitance
Input resistance
RTS, CTS, DTR, DSR, DCD, RI
OFF
ON
Limit
100 k
< 100 pF
Limit
< 100
1nF
100 k to 2.75 V
CMOS level
> 1.93 V
< 0.80 V
37
Advertisement
Table of Contents
