Technical Reference Guide
Compaq iPAQ Family of Internet Devices
First Edition - March 2000
5-5
5.4 SERIAL IN TERFACE
The legacy-light models include a serial interface to transmit and receive asynchronous serial
data with external devices. The serial interface function is provided by the LPC47B277 I/O
controller component that includes a NS16C550-compatible UART.
NOTE: Legacy-free models do not have an externally accessible serial port, but do have
an internal serial header to satisfy the serial port requirements of some operating
systems.
The UART supports the standard baud rates up through 115200, and also special high speed
rates of 239400 and 460800 baud. The baud rate of the UART is typically set to match the
capability of the connected device. While most baud rates may be set at runtime, baud rates
230400 and 460800 must be set during the configuration phase.
5.4.1 RS-232 INTERFACE
On the legacy-light system, the UART is associated with a DB-9 connector that complies with
EIA standard RS-232-C. The DB-9 connector is shown in the following figure and the pinout of
the connector is listed in Table 5-5.
Figure 5-3. Serial Inter face Connector (Male DB- 9 as viewed from rear of chas sis)
Table 55. DB-9 Serial Connector Pinout
Table 5-5.
DB-9 Serial Connector Pinout
Pin Signal Description Pin Signal Description
1 CD Carrier Detect 6 DSR Data Set Ready
2 RX Data Receive Data 7 RTS Request To Send
3 TX Data Transmit Data 8 CTS Clear To Send
4 DTR Data Terminal Ready 9 RI Ring Indicator
5 GND Ground -- - - --
The standard RS-232-C limitation of 50 feet (or less) of cable between the DTE (computer) and
DCE (modem) should be followed to minimize transmission errors. Higher baud rates may
require shorter cables.