Motorola CML12S-DP256 User's Guide download pdf (Page 18)

CML12SDP256 10/10/02

The 1,4,6,7,8, and 9 pins provide RS232 flow control and status. These are connected on the

on the bottom of the development board to provide NULL status to the host. User may isolate

pins and provide flow control or status connection to the host by applying HCS12 I/O signals

and RS232 level conversion.

P_COM2

P_COM2 is a 3 pin header that provides the HCS12 SCI1 serial port translated to RS232

signal levels. A solder cup DB9 style connector may be installed with wires and connector to

apply this channel. JP2 option will isolate the SCI RXD pin from the transceiver.

P_COM2 pin connections:

Pin 1 = TXD

Pin 2 = RXD

Pin 3 = GND / common

CAN PORT

This port provides a CAN Bus interface associated with HCS12 CAN channel 0. The port has

a CAN Transceiver (Philips PCA82C250) capable of up to 1M Baud data rate. The user may

isolate the HCS12 CAN channel 0 from the transceiver by CUT-AWAY option 5.

CAN Port Connections

GND

CAN-H

CAN-L

+5V

The CAN Port connector provides an interface to the MSCAN12

channel 0 in the HCS12 microcontroller.

CAN BUS TRANSMIT ENABLE

The CAN port transceiver transmit driver is enabled for maximum drive and minimum slew rate

by default. The drive and slew rate may be adjusted by cutting CUT-AWAY #6 and adding a

1206 size surface mount resistor, see the PCA82C250 data sheet for more information.

CAN Bus transceiver transmit enable control can be applied to the port by the RS tie pad.

The user should select an available HCS12 I/O port to perform the transmit enable function

and connect it from the MCU_PORT pin to RS pad as required. The CUT_AWAY #6 must be

open to apply transmit enable control. The transmit enable signal to the CAN transceivers is

active logic low.

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Motorola CML12S-DP256 User's Guide Page 18