Freescale Semiconductor
13
Communications signals Tx/Rx route to connector J1 for use off-module if desired. When
using these signal to drive off-module RS-232 devices or when attempting alternate
communications protocols such at IrDA or LIN, the user should disconnect the on-board RS-
232 transceiver. The COM_EN header block allows the user to selectively disable each of the
4 communications signals.
Figure 4: COM_EN Header
1 2
TX
Enable/Disable TX to transceiver
3 4
RX
Enable/Disable RX to transceiver
COM_EN
COM Connector
A standard 9-pin Dsub connectors provide external connection for COM1. The Dsub shell is
connected to board ground through a ferrite bead. The ferrite bead provides noise isolation on
the RS-232 connection. The figure below details the DB9 connector.
Figure 5: COM Connector
1
6
TXD
2
7
RTS
RXD
3
8
CTS
4
9
NC
GND
5
Female DB9 connector that interfaces to the MCU internal SCI0 serial port via
the RS232 transceiver. It provides simple 2 wire asynchronous serial
communications without flow control. Flow control is provided at test points
on the board. A straight-through cable is used to connect the module to a DTE
device such as a host PC.
Pins 1, 4, and 6 are connected together.
Pins 7 and 8 are connected together.
