York 00497VIP manual Bios Eprom U45

Service

Program Jumper JP5) to high voltage AC (500 to 1500VAC). This high voltage AC is applied to the lamp to cause it to illuminate. The Backlight is turned on and off with the “Enable Backlight” (J6-5) signal. The position of Program Jumper JP4 determines whether this is a +12VDC or +5VDC signal. In some displays, the Backlight turns on when this signal transitions from low to high; others turn on when it transitions from high to low. The position of Program Jumper JP3 determines the transition that will occur when the Display Controller outputs the “Enable Backlight” signal. Program Jumper JP3 must be positioned accord- ing to the Display manufacturer’s requirement.

Under Program control, the Display Controller controls the Backlight brightness via the Lamp Dimmer circuit. In order to extend the life of the backlight lamp, the lamp brightness is driven to 50% brightness after 10 minutes of Keypad inactivity. At this brightness level, the Display can still be read. Subsequently, when Keypad activity is detected (i.e. a Keypad key is pressed), the lamp is driven back to full brightness (100% brightness). Some display manufacturers require a variable voltage to vary the brightness; others require a variable resistance. Program Jumpers JP7 and JP8 allow either method to be used. The Lamp Dimmer is an integrated circuit that is the electrical equivalent of a 10K ohm potentiometer with 100 positions or steps (ref. Fig. 34). The Display Controller controls the position of the potentiometer. The Lamp Dimmer varies the brightness of the Backlight by applying either a variable voltage (0-5.0VDC) or a variable resistance (0-10K ohms), to the Backlight Inverter Board. If Program Jumpers JP7 and JP8 are installed, the Lamp Dimmer output is a variable voltage; if both are removed, the output is a variable resistance. The Lamp Dimmer outputs “Brightness Control Wiper” (J6-7) and “Brightness Control -“ (J6-8) to the Backlight Inverter Board. If configured for variable voltage output, the voltage between J6-7 and J6-8 can be varied from 0 (100% brightness) to 5.0VDC (0% brightness). If configured for variable resistance, the resistance between J6-7 and J6-8 would vary from 0 ohms (0% brightness) to 10K ohms (100% brightness).

The PC-104 Port (J16 & J17) is an industry standard arrangement of two connectors that allows the stacking of 3.6 x 3.8 inch printed circuit boards (PC-104 Modules) on the Microboard. The circuits on these boards have access to the Microboard’s address/data bus, and therefore become an extension of the Microboard. This provides expansion of the Microboard’s capabili- ties without redesigning or changing the size of the Microboard. PC-104 Modules are not used in all Remote Control Center applications.

System temperatures, in the form of analog DC voltages from temperature thermistors, are input to the MUX (multiplexers). Under Program control, the Micro selects these values, one at a time, for input to the Analog to Digital (A/D) converter. As each one is selected, it is passed to the A/D Converter for conversion to a 12-bit digital word that is then input in parallel form to the Micro. The Micro stores each value in the DRAM for display requests, further processing or Serial Port transmission. Each value is also stored in the BRAM for History data.

Service Replacement: Microboards are supplied as Service Replacement parts without the following components:

•BRAM (U52)

•Flash Memory Card (U46)

•BIOS EPROM (U45)

Upon receipt of the replacement Microboard, remove these components from the Board being replaced and install in the replacement Board. Although these components have YORK Part Numbers as listed in the Parts List and can be individually replaced, it is recommended that these existing components be used in the new Board since the BRAM memory device contains all of the programmed setpoints.

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