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CML12SDP256 10/10/02
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CAN BUS TERMINATION
The CAN port provides RC11,12, and 13 1206 SMT size termination resistors on the bottom of
the CML12Sxxx board that are not installed at the factory. The termination resistors provide
optional bias and termination impedance for the CAN bus connected to the CAN Port. Type of
wire media, data rate, length of wire, and number of CAN bus nodes can all effect the
requirement or value of the termination for the CAN bus. User should refer to particular
application for termination requirements.
RC11 CAN-H Bias Resistor: Provides bias to ground potential.
RC12 CAN-L Bias Resistor: Provides bias to +5V potential.
RC13 CAN Termination Resistor: Provides end point termination between CAN-H and CAN-
L signal.
P1 - P4 HCS12 Header Ring
P1 - P4 provide a header ring for all I/O of the HCS12 device. These connectors are not
installed. User should refer to the CML12S board schematic diagram for connector pin
connections. All HCS12 I/O is available from the other I/O Ports on the board.
LCD_PORT
The LCD_PORT interface is connected to the HCS12 SPI-0 port and applies a serial shift
register to convert the data to parallel interface for LCD input. This is required due to the fast
timing characteristics of the HCS12 data bus and the slow timing of the standard LCD
Modules. Example LCD Port assembly language driver software is provided on the support CD
to demonstrate typical LCD module operation using this technique.
The interface supports all OPTREX DMC series and similar displays with up to 80 characters
in 4 bit bus mode and provides the most common pinout for a dual row rear mounted display
connector. The LCD module VEE or contrast potential is 0 Volts on this board. The LCD
module type should be TN (Standard Twist) style and Reflective to support this VEE potential.
The Axiom Mfg. HC-LCD is also compatible. The LCD Module is configured in a Write only
mode, it is not possible to read current cursor position or the busy status back from the
module.
LCD_PORT Connector
+5V 2 1GND
RS 4 3 VEE-GND
EN 6 5R/W-GND
DB1 8 7DB0
DB3 10 9DB2
DB5 12 11 DB4
DB7 14 13 DB6
SPI data bit definitions to LCD Port:
D0 - D3 = DB4 - 7, LCD data
D4 - D5 = Spare pins S1 and S2, not connected
D6 = RS, 0 = LCD Command, 1 = LCD Data
D7 = EN, 1 = LCD enable.
DB0 -DB3 are not applied and have 10K pull-down
resistance.
NOTES: