I don't know anything about these protocols, but I am curious. Are these used internally in the machine (ie to connect the coin mechanism to the dispensing mechanism) or externally (so you could connect a test instrument to the machine to read fault codes)? Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams Martin Leg wrote: > There are two different serial protocols that vending machines use: > MDB and Executive. > Does someone know how them work? -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu