MicroBlaze Development Kit Spartan-3E 1600 Edition User Guide 59UG257 (v1.1) December 5, 2007 www.xilinx.comRChapter 7RS-232 Serial PortsOverviewAs shown in Figure 7-1, the MicroBlaze Development Kit board has two RS-232 serialports: a female DB9 DCE connector and a male DTE connector. The DCE-style portconnects directly to the serial port connector available on most personal computers andworkstations via a standard straight-through serial cable. Null modem, gender changers,or crossover cables are not required.Use the DTE-style connector to control other RS-232 peripherals, such as modems orprinters, or perform simple loopback testing with the DCE connector.Figure 7-1 shows the connection between the FPGA and the two DB9 connectors. TheFPGA supplies serial output data using LVTTL or LVCMOS levels to the Maxim device,which in turn, converts the logic value to the appropriate RS-232 voltage level. Likewise,the Maxim device converts the RS-232 serial input data to LVTTL levels for the FPGA. Aseries resistor between the Maxim output pin and the FPGA’s RXD pin protects againstaccidental logic conflicts.Hardware flow control is not supported on the connector. The port’s DCD, DTR, and DSRsignals connect together, as shown in Figure 7-1. Similarly, the port’s RTS and CTS signalsconnect together.
