Refer to Figure 3-40 in Example 3-23. Inputs A 7 through A 0 are address inputs that

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Refer to Figure 3-40 in Example 3-23. Inputs A7 through A0 are address inputs that are supplied to this circuit from outputs of the microprocessor chip in a microcomputer. The eight-bit address code A7 to A0 selects which device the microprocessor wants to activate. In Example 3-23, the required address code to activate the LCD was A7 through A0 = 111111102 = FE16.

Modify the circuit so that the microprocessor must supply an address code of 4A16 to activate the LCD.


Data from Example 3-23

The logic circuit in Figure 3-40 is used to enable the liquid crystal display (LCD) of a handheld electronic device when the microcontroller is sending data to or receiving data from the LCD controller. The circuit will enable the display when LCD = 1. Determine the input conditions necessary to enable the LCD.


Figure 3-40

A A A3 A4 A5 As A7 A IN OUT 74HC30 74HC02 W X Note: All gates are CMOS. 74HC32 74HC02 LCD

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Digital Systems Principles And Application

ISBN: 9780134220130

12th Edition

Authors: Ronald Tocci, Neal Widmer, Gregory Moss

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