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MC14497P bảng dữ liệu(PDF) 4 Page - Motorola, Inc |
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MC14497P bảng dữ liệu(HTML) 4 Page - Motorola, Inc |
4 / 8 page MC14497 MOTOROLA 4 PIN DESCRIPTIONS E1 – E8 Row Inputs (Pins 1, 2, 10, 11, 14, 15, 16, 17) Under idle conditions, these inputs are held high by inter- nal pull–up resistors. As soon as a key is pressed, a logical 0 on that particular line signals to the circuit that a key has been selected. After a delay of 20 ms, the internal register is loaded with the code word for the key selected. E9 Row Input (Pin 3) This is a special programming input and when connected to the appropriate scanner output via a diode, it will modify the transmitted output according to Table NO TAG. In Table NO TAG, the figures in brackets (FK1, etc.) refer to the switches shown in the Block Diagram and Figure 3. If only one option is required, the diode may be omitted. The connections shown in Table NO TAG may be made in any combination. Although E9 is a row input, forcing this line low will not acti- vate the circuit. A1 – A4 Scanner Outputs (Pins 4 – 7) Under idle conditions, these outputs are held low, logical 0. When a key is pressed, the circuit is activated and the oscil- lator will start and release the outputs (see Figure 5). OSCin, OSCout Oscillator Input and Oscillator Output (Pins 12, 13) These pins are designed to operate with a 500 kHz ceram- ic resonator or a tune LC circuit. It is important that a ceramic resonator and not a filter be used here, as the oscillator fre- quency cannot be guaranteed if a ceramic filter is used. SIGNAL OUT Signal Output (Pin 8) This output provides the modulating signal ready to drive the modulation amplifier. If required, the transmitter can be used as a keyboard encoder for direct use with a receiver. In this case, the AM option is selected, the output inverted, and fed directly to the receiver’s signal input pin. Figure 3. 64–Key Keyboard E1a E1 E2a E2 E3a E3 E4a E4 E5a E5 E6a E6 E7a E7 E8a E8 17 2 1 16 15 14 10 11 9 18 VSS VDD 3 13 12 A1 7 A2 6 A3 5 A4 4 FK2 FK1 E9 C1 C2 NOTE: Maximum key contact resistance = 1 k Ω. Figure 4. Transmitted Waveforms and Timing (Not Drawn to Scale) START BIT A B C D E F f2 f3 f3 f2 f3 f2 f3 f2 f3 f1 f1 f1 f1 f1 f1 INSTRUCTION FSK AM ONE WORD DEBOUNCE KEY WORD 20 ms 9 ms 99 ms |
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