Also, we can interface several memory chips to a single 8085 microprocessor, until and unless their combined size does not exceed 64 kB. We can interface a memory chip of size less than that too. The memory address space of the 8085 (i.e., the range of memory addresses that can be addressed by the 8085) takes values from 0000H (A 0-A 15, all bits are zero) to FFFFH (A 0-A 15, all bits are one) when represented in hexadecimal form. So a maximum of 64KB (=2 16 Bytes) of memory locations can be interfaced with it. And each unique address refers to a memory block containing 8 bits or 1 byte of space. So, the total number of addresses that can be generated on a 16-bit address bus will be 65,536. Each bit can take the value of either 0 or 1. External memory support in 8085Īn 8085 microprocessor has a 16-bit address bus (A0-A15). Now the question is how do we connect a memory chip to the 8085 and manage the interactions between the two chips? That is what we are going to explain in this post. So we need to attach external memory chips. But we know that, unlike microcontrollers that have a certain amount of built-in memory, microprocessors do not have their own memory except for a few registers. In one of our previous posts, we have discussed how the 8085 reads from and writes into memory.
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