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HDLS-1414 Datasheet(PDF) 7 Page - AVAGO TECHNOLOGIES LIMITED |
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HDLS-1414 Datasheet(HTML) 7 Page - AVAGO TECHNOLOGIES LIMITED |
7 / 9 page 7 Display Internal Block Diagram Figure 2 shows the HDLX-1414 display internal block diagram. The CMOS IC consists of a 4 x 7 Character RAM, a 128-character ASCII decoder and the refresh circuitry necessary to synchronize the decoding and driving of four 5 x 7 dot matrix characters. Four 7-bit ASCII words are stored in the Character RAM. The IC reads the ASCII data and decodes it vita the 128-character ASCII decoder. This decoder includes the 64-character set of the HPDL-1414, 32 lower case ASCII symbols, and 32 foreign language symbols. Data Entry Figure 1 shows a truth table for the HDLX-1414 display. Address inputs A0 and A1 are used to select the digit location in the display. When A0 and A1 are both logic low, data is loaded into the right most character. Data inputs D0–D6 are used to load information into the display. Data is latched into the given character address on the rising edge of the \WR signal. Data and Address inputs must be held stable during the write cycle to ensure that correct data is stored in the display. Mechanical and Electrical Considerations The HDLX-1414 is a 12-pin DIP package that can be stacked to create a character array of any size. The display is designed to operate reliably in –40˚C to +85˚C ambient temperatures. Electrical Description Pin Function Description \Write (\WR, Pin 3) WR must be logic 0 to store data in the display. Address Inputs A0 and A1 select a specific location in the display memory. Address 00 accesses the far right (A1 and A0, Pins 4 and 5) character, and address 11 accesses the far left position. VDD (Pin 6) VDD is the positive power supply input. Ground (GND, Pin 7) Ground is the display ground. Data Inputs D0–D6 are used to specify the input data for the display. (D0–D6, Pins 1, 2, 8-12) The HDLX-1414 is assembled by die attaching and wire bonding 140 LEDs and a CMOS IC to a high tempera- ture printed circuit board. A polycarbonate lens is placed over the PC board, creating a protective air gap over the LED wire bonds. Backfill epoxy environmentally seals the display package. This package construction makes the display highly tolerant to temperature cycling and allows wave soldering. ESD and Latchup Protection The inputs to the CMOS IC are protected against static discharge and input current latchup. However, for best results, standard CMOS handling precautions should be used. Prior to use, the HDLX-1414 should be stored in antistatic tubes or conductive material. During assembly a grounded conductive work area should be used, and assembly personnel should wear conductive wrist straps. Lab coats made of synthetic material should be avoided since they are prone to static charge build-up. Input current latchup can be caused when the CMOS inputs are subjected either to a voltage below ground (Vin < ground) or higher than VDD (Vin > VDD) and when a high current is forced into the input. To prevent input current latchup and ESD damage, unused inputs should be connected either to ground or to VDD. Voltages should not be applied to the inputs until VDD has been turned on, and high transient input voltages should be eliminated. \WR A1 A0 D6 D5 D4 D3 D2 D1 D0 Function 1 X X X X X X X X X No Change 0 0 0 Digit 0 ASCII Data (Right Most Character) 0 0 1 Digit 1 ASCII Data 0 1 0 Digit 2 ASCII Data 0 1 1 Digit 3 ASCII Data (Left Most Character) 0 = Logic 0; 1 = Logic 1; X = Do Not Care. Figure 1. Display truth table. Write to Character RAM |
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Similar Description - HDLS-1414 |
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