8085 Microprocessor

2 Hardware Model & Programming Model

There are two major segments in hardware model. In first segment there are Accumulator,ALU,Flags,Instruction decoder. And in second segment there are 8 bit and 16 bit register.

There are three buses which is used for various interconnections that are 16- bit unidirectional address bus,8 -bit bidirectional data bus and control bus.

Fig. Programming model

It consist of some segments of the ALU and the registers.this model includes the information that is critical in writing assembly language programs.

The processor has seven 8-bit registers accessible to the programmer, named A, B, C, D, E, H, and L, where A is the 8-bit accumulator and the other six can be used as independent byte-registers or as three 16-bit register pairs, BC, DE, and HL, depending on the particular instruction. Some instructions use HL as a (limited) 16-bit accumulator. As in the 8080, the contents of the memory address pointed to by HL could be accessed as pseudo register M. It also has a 16-bit program counter and a 16-bit stack pointer to memory.

There are flag registers also in programming model. Which are five flip flops which are set or reset after an operation according to data conditions.