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