SYSTEM CONNECTOR INTERFACE
38
LZT 123 8020 R1A
•
UART2 behaves as a general-purpose serial data link. For
example, it can be used for GPS, downloading software and
receiving logging information.
•
UART3 behaves as a general purpose serial data link. It is
the only UART that can be used by the embedded
application.
Note!
Digital 2.75V 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.
Note!
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
RTS, CTS, DTR, DSR, DCD,
CMOS level
< – 3 V
1
OFF
> 1.93 V
> + 3 V
0
ON
< 0.80 V
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.
Parameter Limit
Application load resistance
<
100 k
Ω
Application load capacitance
< 100 pF
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