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www.digilentinc.com
Revision: June 6, 2012
Note: This document applies to REV B of the board.
215 E Main Suite D | Pullman, WA 99163
(509) 334 6306 Voice and Fax
Doc: 502-068 page 1 of 2
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
Analog
Devices
ADM3232E
RS232
Transceiver
DCE Connector
DB9
Pins 1,4,6 are tied
for handshaking.
NC
16
49
8
37
2
5
J1
1
2
3
4
5
6
CTS
RTS
TXD
RXD
JP1JP2
GND
VCC
RS232 Module Block Diagram
Overview
The PmodRS232 Converter Module Board (the
RS232 module) translates voltage from the
logic levels used by Digilent system boards to
the RS232 voltage used for serial
communications.
The RS232 module creates a two-way I/O
exchange by converting RS232 voltage to logic
level voltage and converting logic voltage to
RS232 voltage. RS-232 voltage levels are -3 to
-12V for a logic ‘1’, and +3 to +12 for a logic ‘0’.
The RS232 module is configured as a data
communications equipment (DCE) device. It
connects to data terminal equipment (DTE)
devices, such as the serial port on a PC, using
a straight-through cable.
Features include:
an Analog Devices ADM3232E RS232
transceiver
a DB9 connector and 6-pin header
transmit and receive data functions
optional RTS and CTS handshaking
functions
small form factor (1.00” x 1.30”).
Functional Description
The RS232 module provides two transmit
buffers and two receive buffers. A transmit
buffer converts a logic-level signal on its input
to an RS232 voltage-level signal on its output.
A receive buffer converts an RS232 voltage-
level signal on its input to a logic-level signal
on its output.
The RS232 module can be configured as
either a 3-wire DTE serial port (with one
transmitter for transmit-data signals, one
receiver for receive-data signals, and a signal-
ground connection), or as a 5-wire DTE serial
port with an additional transmitter and receiver
for RTS and CTS handshaking signals,
respectively.
The RS232 module is designed to work with
either Digilent programmable logic system
boards or embedded control boards. Most
Digilent system boards (like the Basys, Nexys
or Cerebot) have 6-pin connectors that allow
the RS232 module to plug directly into the
PmodRS232 Reference Manual
Digilent, Inc.
www.digilentinc.com
www.digilentinc.com page 2 of 2
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
system board or to connect via a Digilent 6-pin
cable.
Some older Digilent boards may need a
Digilent Module Interface Board (MIB) and a 6-
pin cable to connect to the RS232 module. The
MIB plugs into the system board and the cable
connects the MIB to the RS232 module.
RS232 Module Connector J1
The RS232 module is wired as a DTE device.
RS232 signals are named from the perspective
of the DCE. The TXD signal carries data from
the DCE to the DTE, therefore, the TXD signal
on pin 3 is connected to the output of a
receiver and should be connected to the
receive input of a UART on the system board.
Similarly, the RXD signal carries data from the
DTE to the DCE and is connected to the input
of a transmitter on the RS232 module and
should be connected to the output of the UART
on the system board.
The CTS signal on pin 1 can be connected to
the input of a transmitter and the RTS signal
on pin 2 can be connected to the output of a
receiver. These connections are made using
jumper blocks JP1 and JP2, as described
below.
Digilent embedded control boards, like the
Cerebot, have one or more connectors with the
UART signals configured correctly for direct
connection of the RS232 module. On Digilent
programmable logic boards like the Basys or
Nexys, a UART must be defined in the logic of
the FPGA or CPLD and the appropriate signal
connections must be defined to connect the
UART to appropriate connector pins.
Using Jumper Blocks JP1 and JP2
Jumper blocks JP1 and JP2 are used to
configure the RS232 module for either 3-wire
or 5-wire operation. Pins 1 and 2 of JP1 are
connected to pins 1 and 2 of connector J1,
respectively. Pins 1 and 2 of JP2 are
connected to the CTS transmitter and the RTS
receiver, respectively.
To configure the RS232 module as a 3-wire
DTE with no handshaking, place a shorting
block across the two pins of JP2 and ensure
there’s no shorting block on JP1. This loops
RTS back to CTS on the RS232 side of the
module and leaves pins 1 and 2 unconnected
on J1.
To configure the RS232 module as a 5-wire
DTE with RTS/CTS handshaking, place a
shorting block across pin 1 of JP1 and pin 1 of
JP2, and place another shorting block across
pin 2 of JP1 and pin 2 of JP2. This connects
the CTS transmitter to pin 1 of J1 and the RTS
receiver to pin 2 of J1.