M 6 8 E V B 9 1 2 C 3 2
0 5 / 1 5 / 0 3
12
COM1 (SCI) Port
COM1 is a standard RS-232 compatible serial port controlled by the 9S12C32 SCI port. The
RX_EN, CTS_EN, and RTS_EN option jumpers provide HCS12 I/O port connection to the
COM1 port on the EVB board. This allows the user to apply the provided communication
transceiver or to apply the associated I/O to other purposes. The option jumper positions
should be reviewed first if any operational problems are encountered with the COM1 or HCS12
SCI port.
COM1 Connection
The COM1 port provides standard 9 pin connection with RS232 type interface to the HCS12
SCI peripheral. Refer to the options for enabling the HCS12 signals applied to these ports.
The COM1 port is applied by default with the Debug Monitor. The HCS12 SCI module TxD
and RxD signals are converted to RS232 levels by U11 and provided to the DB9 serial
connectors. Following is the DB9S connection reference.
COM1
1
1
X
TXD
2 6
6
RXD
3 7
7 CTS in
4
4 8
8 RTS out
GND
5 9
9
Female DB9 connector that interfaces to the HCS12
internal SCI serial port via the U11 RS232 transceiver.
1,4,6 connected
Notes:
1) COM1 pins 1, 4, and 6 can be isolated from each other on the bottom of the EVB board
under the COM1 connection test pads by cutting the associated test pad circuit trace.
2) COM1 pin 8 (RTS) is pulled to the active flow control enabled level when the RTS_EN
option is open. (flow is enabled)
3) Test pad connections are provided for COM1 pins 1-4 and 6-9. The test pads are located
behind the COM1 connector on the EVB board.
RX_EN Option
The RX_EN option jumper will isolate the HCS12 SCI RxD pin (PS0) from the RS-232
transceiver (U11). This allows the HCS12 I/O pin or Transceiver output to be applied to some
other user application. Note that this option jumper must be installed for monitor
communication.
RTS_EN and CTS_EN Options
These options allow the user to apply RS-232 serial flow control on the COM1 port. Note that
the Monitor communication does not support the flow control operation and that if the user
application has configured the RTS output disabled the monitor will not operate.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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