Intro to Microprocessors

My take on learning microprocessors: 1) Pick a reasonable processor. An 8085, Z80, 6502, or 680x is reasonable. A Pentium III is not. 2) Read the data sheets. Get an idea of what the timing requirements are, how you interface to the timing, address, data, and I/O. Don't rely on other people's schematics unless you absolutely have no idea what you should do. Make sure after using other people's schematics that you do under- stand what they did and why. 3) Build a simple circuit on a large wire-wrap board. Include the processor, minimal ROM, minimal RAM, and a simple I/O port with eight LEDs attached. Write a small program to write different values to the LEDs. Verify they are correct. Use a wire-wrap board with enough room to add lots of stuff later. You'll be glad of the room later. 4) Add a serial I/O port. Write a small program to read data from a terminal (or equivalent) and echo the data back. 5) Start extending the program to write your own machine language monitor. You've got the I/O routines. Add the functions one or two at a time, testing along the way. You'll want to add memory read, memory write, memory fill, register read, register write, port read, port write, program start, breakpoints, but not a disassembler or assembler. Learn the machine code first. Later you can add the assembler/disassembler. 6) Add some kind of program storage, either out through the serial port, through an additional serial port (adding another shouldn't be difficult), or some other way. Be creative. 7) Go off on your own. Experiment. Add some A/D converters. Add some D/A converters. Whatever you find interesting. But the most important point to remember is to understand the whats and whys of everything you do. Step (5) is probably the one you'd be most tempted to cheat on, but it really isn't that difficult to roll your own. If you'd like, after you've got the basic functions going, you can either add features from some other monitor program, or use a completely different monitor program modified to work with your system, but definitely write the basics yourself so you know what's going on. Any comments? -- Eric Dittman dittman(a)dittman.net