Simple peer to peer network?

Since it's a C64, I assume that the ports are polled rather than interrupt driven I/O? Flow control might be a problem if these machines are doing other things at the same time. I see two potential architectures.... The easiest is a ring with packet forwardings. Each machine has its output connected to one machine and its input connected to another. This is probably the simplest hardware wise and software wise. It's also the slowest. When a packet comes in, its destination address is checked against the current machines address. If it doesn't match, it is forwarded to the next machine. No collision detection is necessary. One potential problem is that a packet with a bad address can circulate forever unless you have a way of detecting it. Next, there's a token ring where all of the outputs are connected to all of the inputs, except perhaps not the input on the same machine. For 64 machines you're going to need external electronics to clean up the signals, since I doubt that a single output can drive 64 inputs. The other potential problem is connecting inputs together. You are going to need to prevent non-transmitting inputs from frying themselves probably by tristating any input on a machine that doesn't have the token. Even if you have them tristated you are going to want current limiting protection so you don't blow out the ports when a problem happens. I doubt that the C64 serial ports are specified to survive having multiple transmitters on the same line. For protocol, I'd go with a modified SLIP, since it's well specified, small enough to implement on an 8 bit processor, includes appropriate escape characters, the code is everywhere and it's easily modified. We've used it for serial buses on spacecraft. On Jan 28, 2008 7:30 PM, Jim Brain <brain at jbrain.com> wrote: