Thanks and Good points Gary, Could I add… The default mode for the Z80 (& 8086 & 80386) monitors is NO IOBYTE port present. I.E. the monitor will always read port EF as 0FFH. This will cause the monitor to expect the console I/O to come from the Propeller Console I/O ports (0 & 1) or whatever other arrangement you have programmed in the appropriate modules in your system. The “IOBYTE” concept arose from Roger Amadon’s Zapple’s monitor at TDL back in the late 70’s. It was carried on to CPM for redirection I/O. I have used some bit’s to do other things with CPM as well, but its main use is in debugging hardware with the 8086 and later CPU’s. You really have to be very careful with jumpers for earl y PROMS. See here for a summary:- http://s100computers.com/My%20System%20Pages/PROM%20Board/PROM%20Board.htm As the years go by we are getting better (I think) at laying out and labeling new boards. These days IC’s have their numbers outside the footprint. Jumpers have their function(s) in small fonts beside them and polarized caps/LED’s have their + terminal as a square pad. That said, because of the way freerouter works in finding the shortest possible routes, the pin 1 of jumpers, LED, caps and resistor arrays is NOT the same across the board. Pin 1 is always the square pad but its orientation varies. Be very careful with this. A miss-orientated resistor array is very difficult to detect/debug/remove. Finally I would like to point out that while I try to write-up build instructions is a step by step manner, errors do creep in. Don’t regard the write-up as “Gospel” is you notice a serious error please let me know. John From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Gary Kaufman I don't have the sophistication/knowledge of may folks here, but at least for me, getting an initial system working was a challenge. Hi everyone. I just finished building the Z80 board and I am having some problems, so I am hoping that some of you have some ideas. My system is the following: V2-S100 Z80 Master CPU board 4Meg static RAM board Prop I/O board I have the Z80 board jumpered as master. I also have a simple switch for reset. The RAM board is set for 1Meg only at 0000H. -- |