Modem User Manual

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5.11.1 UART1
Pin Name Direction Function
32 DSR1 Output Data Set Ready (UART1)
36 RI Output Ring Indicator
37 DTR1 Input Data Terminal Ready (UART1)
38 DCD1 Output Data Carrier Detect (UART1)
39 RTS1 Input Ready To Send (UART1)
40 CTS1 Output Clear To Send (UART1)
41 DTM1 Input Data To Module from host (UART1)
42 DFM1 Output Data From Module to host (UART1)
UART1 is a full featured Universal Asynchronous Receiver Transmitter providing full-
duplex asynchronous communication.
UART1 has the following features:
• 32 bytes of FIFO for both receive and transmit
• FIFO threshold interrupts
• 1 start bit, 7 or 8 data bits, 1 optional parity bit, 1 or 2 stop bits
• Programmable baud rate
• Auto-configuration mode with auto-baud and auto-format operation
• Hardware flow control
• Software flow control.
UART1 signals replicate a 9-pin RS232 (V.24) serial port. However, UART1 signal
levels are not compliant with the RS232 (V.28) standard. Conversion between the
wireless modem CMOS levels and RS232 levels can be achieved using a standard
interface IC, such as the Maxim Integrated Products MAX3237. The relationship
between the levels is shown in the following table:
DTM, DFM RI,RTS,CTS,DSR,DTM,DCD RS232 level GR64 level
1 OFF <-3V VREF-0.4V
0 ON >+3V 0.4V
5.11.2 Serial Data Signals (DTM1, DFM1)
The default baud rate of the UARTs is auto-baud. Baud rates of between 600 bauds
to 460 kbauds are possible. The wireless modem also supports 3GPP TS 27.010
multiplexing protocol, which starts when the appropriate command is sent.