On the BASIC Stamp II, how does the ATN (Attention) pin work?
The ATN pin is used strictly for programming the BASIC Stamp II and should not be connected to anything other than the DTR pin of the programming connector. The ATN pin is an input and has an inverse relationship with the reset (RES) pin. When the ATN pin is left unconnected or is driven low it causes the RES pin to go high (allowing the BASIC Stamp II to function properly). When the ATN pin is driven high it causes the RES pin to go low (performing a hardware reset on the BASIC Stamp II). The BASIC Stamp II editor software toggles this pin from low to high and then low again at the start of the programming process to perform a hardware reset on the BASIC Stamp II and begin the bi-directional programming communication. It is important to be aware of a particular artifact of the DTR pin on a standard serial port: upon port selection by standard software (terminal packages, development tools, etc.), the DTR pin is driven high by default. If the same connections for programming the BASIC
