The 8085 Microprocessor and Memory Addressing

The 8085 microprocessor is an 8-bit microprocessor that was widely used in early personal computers and other electronic devices. It has a 16-bit address bus, which means it can address up to 2^16 (64K) memory locations.

However, the 8085 microprocessor has a limitation in terms of the amount of memory it can directly access. It can only directly access a maximum of 64K bytes of memory. In order to access more memory, additional circuitry is required.

Memory Banking

Memory banking is a technique used to overcome the limitation of the maximum addressable memory by the microprocessor. It involves dividing the memory into multiple banks and using external logic to switch between these banks.

In the case of the 8085 microprocessor, a technique called bank switching is used. The memory is divided into 16K byte banks, and the microprocessor can access each bank individually by switching between them.

Calculating the Number of Address Lines

To determine the number of address lines required to access a 16K byte memory bank, we need to calculate the number of addressable memory locations in a 16K byte bank.

1. One memory location requires one addressable location, so the number of addressable locations in a 16K byte bank is 16K.

2. Since the microprocessor has a 16-bit address bus, it can address up to 2^16 (64K) memory locations.

3. To address 16K memory locations, we need to find the minimum number of address lines required to represent 16K.

4. The formula to calculate the number of address lines required is given by n = log2(N), where n is the number of address lines and N is the number of addressable locations.

5. Substituting N = 16K = 16 * 1024, we get n = log2(16 * 1024) = log2(2^4 * 1024) = log2(2^4) + log2(1024) = 4 + log2(2^10) = 4 + 10 = 14.

Therefore, the number of address lines required to access a 16K byte memory bank in an 8085 microprocessor is 14.