Compaq dc7800 Technical Reference Guide: HP Compaq dc7800 Series Business Desk - Page 60
Serial Interface
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Input/Output Interfaces 5.5 Serial Interface Systems covered in this guide may include one RS-232-C type serial interface to transmit and receive asynchronous serial data with external devices. Some systems may allow the installation of a second serial interface through an adapter that consists of a PCI bracket and a cable that attaches to header P52 on the system board. The serial interface function is provided by the SCH5317 I/O controller component that includes two NS16C550-compatible UARTs. 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. The serial interface uses a DB-9 connector as shown in the following figure with the pinout listed in Table 5-4. Figure 5-4. DB-9 Serial Interface Connector (as viewed from rear of chassis) Table 5-4. DB-9 Serial Connector Pinout Pin Signal 1 CD Description Carrier Detect Pin Signal 6 DSR Description Data Set Ready 2 RX Data 3 TX Data 4 DTR Receive Data Transmit Data Data Terminal Ready 7 RTS 8 CTS 9 RI Request To Send Clear To Send 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. 5-6 www.hp.com Technical Reference Guide