Despite what Erik said, if you use a fairly standard (I can't recommend ATMEL) sort of 805x MCU, in a more or less standard package, DIL or PLCC package, you can build it yourself using wire-wrap in about an hour or so, once you have the board, tools and sockets. Be sure to decide beforehand what frequency crystal you'll be using, and ensure it allows you to reach the async baud rate you need in the available timer/counter modes. If you've read and understood the datasheet(s)you should have a working circuit once you find any wiring mishaps, as the design of a single-chipper application is quite trivial. Standard tools will work with nearly any "standard" 805x MCU.

Be sure to use a board with a solid contiguous ground plane throughout, and use #20 or larger wire soldered to the power pins for Vcc, with a small (10 nF) cap at each Vcc power connection to each IC. Keep the connections between the cap's and power rails short (< 1 mm) and be sure that your power supply is able to provide at least 10x, but 100x is better, the calculated Vcc requirement for your board. Be sure, too, that you never have more than 50 mV of noise on the Vcc supply.

RE