COM 1 is connected directly to the Micro. COM 2 through 5 are connected directly to the UART (Universal Asynchronous Receive Transmit). The UART converts the parallel data to serial form for transmission to the peripheral device and converts the incoming serial data to parallel form for use by the Micro. It also generates and processes control signals for the Modem communications (DTR, CTS, DSR, RTS). Under Program control, the Micro instructs the UART of the desired data transmission Baud rate. A crystal oscillator provides the frequency reference. Each port is equipped with two LED’S; a red one indicates when data is being transmitted to the remote device and a green one indicates when data is being received from the remote device. The RS-232 output voltages are industry standard +3 to +15VDC, with +9VDC typical. The RS-485 output voltages are industry standard +1.5 to +5VDC, with +2.5VDC typical. A loopback diagnostic test can be performed on each serial port. This test permits verification of the data transmitted from the serial port. Refer to the “Serial Inputs / Outputs Tests” description in this book for details of these tests. The graphic screens that are displayed on the Liquid Crystal Display are created from preformed graphics and messages that are stored in the Program (FLASH Memory Card), and real-time system operating parameters, such as temperatures. The graphics, message and number data are in the form of digital words. The Display Controller converts this data into display drive signals and sends them to the Display from Microboard J5. The Display has 307,200 pixels arranged in a 640 columns x 480 rows matrix configuration. Each pixel consists of 3 windows; red, green and blue, through which a variable amount of light from the Display backlight is permitted to pass through the front of the display. Imbedded in each window of the pixel is a transistor, the conduction of which determines the amount of light that will pass. The drive signal determines the amount of conduction of the transistor and therefore the amount of light passed through the window. The overall pixel color becomes a result of the gradient of red, green and blue light allowed to pass. The drive signal for each pixel is an 18 bit binary word; 6 for each of the 3 colors, red, green and blue. The greater the binary value, the greater the amount of light permitted to pass. The pixels are driven sequentially from left to right, beginning with the top row. To coordinate the drive signals and assure the pixels in each row are driven sequentially from left to right and the columns are driven from top to bottom, each drive signal contains a horizontal and vertical sync signal.
FORM 50.40-OM2
The Display DRAM is a memory device that supports the operation of the display controller. This device could be either of two types; FPM (fast page mode) or EDO (extended data out) type. Program Jumper JP6 must be positioned according to the type of DRAM device installed in the Microboard; JP6 in - EDO, out - FPM. Refer to Table 2, “Program Jumpers”. Depending upon the requirement, there could be one or two DRAM devices installed in the Microboard. If the design requires only one DRAM, it is installed in socket U27. If an additional one is required, it is installed in socket U25.
During the power-up sequence, the program in the BIOS EPROM reads Program Jumper JP6 to determine the type of Display DRAM installed (as explained above). It also reads wire jumpers PID0 through PID3 (via Microboard J5) on the Display Interface Board to determine the manufacturer of the display (refer to description of Display Interface Board). Each display manufacturer requires a slightly different control. The program in the BIOS EPROM then configures the Display Controller for operation with the actual display that is present.
Different Display manufacturers can require different supply and control voltages for their displays and backlights. Program Jumpers JP 2 through 4 and 5 through 8 must be configured to provide the required supply and control voltages to the display and backlight control. Table 2 lists the required Program Jumper configuration for the Display. Also, a label attached to the Display mounting plate lists the required Program Jumper configuration for that particular Display.
The power supply voltage that operates the Display is provided by the Microboard J5. The position of Program Jumper JP2 determines whether this supply 5 voltage is +5VDC or +3.3VDC. The Display requires a specific power-up and power-off sequencing to prevent damage. During power-up, the supply voltage must
be applied to the Display before the drive signals are applied. Similarly, during power-off sequencing, the display drive signals must be removed prior to removing the supply voltage. The Display Controller applies the supply voltage and data drive signals to the Display in the proper sequence. The Display Controller controls the Display Backlight by applying control signals (from Microboard J6) to the Backlight Inverter Board. The Backlight Inverter Board converts low voltage DC (+12VDC or +5VDC, depending on position of
