Study of microprocessors is an integral part of the engineering programme, when we are taking up a course on electronics or any related discipline. And 8085 is probably the first microprocessor that we get in touch with as a part of the curriculum. Students are usually just given some basic hands-on training using standard boards with a keypad.
Whenever we are dealing with hardware, there is always a chance for it to fail. Moreover, there are some practical concerns while learning microprocessors using boards. If you would like to simultaneously determine the status of all the registers at a time, or analyse the working in varying speed of simulations, a trainer kit may have limitations.
For electronics enthusiasts willing to learn programming of microprocessors, but limited by the availability of trainer kits, there are a handful of simulators available online as open source. In this article, let us have a look at one such 8085 simulator.
The 8085 programming model
8085 processor has a set of seven 8-bit registers including the accumulator and six others, namely, B, C, D, E, H and L. Depending upon applications, the registers other than the accumulator can be used either as independent byte-registers or as 16-bit register pairs.
A 16-bit special-purpose register called program counter is available in the microprocessor. It stores the address of the next instruction to be fetched. A 16-bit stack pointer stores the address of the last byte entered into the stack.