Autonomous I/O Controller

40 AUTONOMOUS I/O CONTROLLER This concluding instalment of the article deals with serial interface hardware at the host computer side, and software command descriptions. EE January 1989 The RS232-to-current loop converter shown in Fig. 12 is the same as that used in the microcontroller-driven power supply. A discussion of its operation and application can be found in Ref. 1. Con- structional details are shown in Figs. 13 (printed-circuit board) and 14 (practical version, ready for fiting inside the hood of a male D-25 connector). Pins 4 and 5 of non-used D9-connectors should be in- terconnected to prevent breaking the cur- rent loop. The adaptor allows up to 6 in- struments to be connected to the bus, but only if the host computer supplies ±12 V at its RS232 outlet. Some com- puters supply only 5 V, which limits the number of instruments that can be con- nected to 2 or maybe 3. Selective addressing The bus structure designed for the automous I/O controller and the microcontroller...