Xilinx MIcroblaze Development Spartan-3E 1600E - Manual (Page 61)

MicroBlaze Development Kit Spartan-3E 1600 Edition User Guide 59
UG257 (v1.1) December 5, 2007 www.xilinx.com
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Chapter 7
RS-232 Serial Ports
Overview
As shown in Figure 7-1 , the MicroBlaze Development Kit board has two RS-232 serial
ports: a female DB9 DCE connector and a male DTE connector. The DCE-style port
connects directly to the serial port connector available on most personal computers and
workstations 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 or
printers, or perform simple loopback testing with the DCE connector.
Figure 7-1 shows the connection between the FPGA and the two DB9 connectors. The
FPGA 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. A
series resistor between the Maxim output pin and the FPGA’s RXD pin protects against
accidental logic conflicts.
Hardware flow control is not supported on the connector. The port’s DCD, DTR, and DSR
signals connect together, as shown in Figure 7-1 . Similarly, the port’s RTS and CTS signals
connect together.