The upper address lines of a 20-bit address are to be connected to the inputs of
ID: 2293387 • Letter: T
Question
The upper address lines of a 20-bit address are to be connected to the inputs of a 10-input PAL to decode memor /O addresses in a systenm The PAL is to generate a low signal when an address in the range 0x82000 0x827FF is selected What do the input values of the PAL need to be for it to output a low? (1, 0, or type in X if input address not used.) The highest order inputs of the PAL should be used first and the lower o connected if not needed ie D9 is connected to A19, D8 to A18, etc...) D7 - D5 = D3 = D2 =Explanation / Answer
Answer :- The address range we have is from-
0x82000 = 1000_0010_0000_0000_0000 to
0x827FF = 1000_0010_0111_1111_1111.
So PAL output must be low when address input having 1000_0010 as starting. So the value of PAL input is-
D9 = 1
D8 = 0
D7 = 0
D6 = 0
D5 = 0
D4 = 0
D3 = 1
D2 = 0
Rest pins are not connected.
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