Interfacing protocols
RS-232 pin signals
XBee-PRO 900HP RF Modem User Guide
17
RS-232 pin signals
The following figure shows the pins used on the female RS-232 (DB-9) serial connector:
The following table describes the RS-232 pin assignments and implementation:
DB-9
pin
RS-232
Name
Description
Implementation
1
DCD
Data-Carrier-
Detect
Connected to DSR (pin 6)
2
RXD
Received Data
Serial data exiting the RF modem (from host)
3
TXD
Transmitted Data
Serial data entering into the RF modem (from host)
4
DTR
Data-Terminal-
Ready
2 – 0xFFFF [x 100 msec]
5
GND
Ground Signal
0x20 – 0x7F
6
DSR
Data-Set-Ready
0 - 4
7
RTS /
CMD
Request-to-
Send/Command
Mode
RTS (request-to-send) flow control: By default, this pin is not
used. To configure this pin to regulate the flow of serial data
exiting the modem, refer to the Serial Communications and RT
command section.
CMD: Refer to Binary Commands and RT Command Sections to
enable binary command programming.
8
CTS
Clear-to-Send
CTS (clear-to-send) flow control –When pin is driven low, UART
host is permitted to send serial data to the modem. Refer to
the Serial Communications and CS Command sections for
more information.
9
RI
Ring Indicator
Optional power input (protection circuitry to prevent back flow
from other power sources internal to the board)
RS-232 wiring diagram
The following figure shows the RS-232 Device DTE Device (male DB-9 connector) wired to a DCE RF
modem (female DB-9) XBee-PRO RF Modem:
